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Len Waldron

The Skinny On Gun 2D Matrix Codes (Take Off The Tin-Foil Hat!)

Love 'em or hate 'em, 2D data matrix codes on guns are likely to stick around.

What Are 2D Data Matrix Codes And What Purpose Do They Serve:

  • The are machine-readable images used to store data, generally laser etched on to the frame of a gun.
  • Manufacturers use them to track the production of a firearm as well ensure the intrigity of serial numbers.
  • Information stored in each code is proprietary to each manufacturer.
  • They do not take the place of the serial number and other information required by the BATF.
  • No, a QR scanner won't read them … sorry.

If you’ve purchased a new firearm recently from one of several major manufacturers, you might’ve noticed a small, square pattern of dots, where before only the company’s engraved name appeared along with the gun’s model and serial number.

2D Matrix Code 5

In an industry where the final turn of a filigree’s orientation from one model year to the next doesn’t go without notice, adding a square of asymmetrical pockmarks is sure to raise eyebrows. And to no surprise, it did, too.

As more firearms appeared on the market with these marks, discussion boards lit up, recoiling and opining endlessly on the illegible and unwelcome addition. Many views are almost comical if not misinformed, but make no mistake: Your eyes do not deceive you—something is afoot.

What is a Dot Peen Marking?

A dot peen marking is an image created using what’s known as stylus pin marking, micro pin marking, or percussion marking device to create a succession of dots that form digits, text, logos, and two-dimensional (2D) Matrix Codes. The latter being the most recent and certainly most cosmetically offensive. As a gun owner, you’ve slowly habituated to this technology without knowing it.

Several firearm companies began printing serial numbers using this technology some years ago. In recent years, lasers took the place of impact tools to create these marks. Most marks simply look like letters and numbers made from a series of dots. However, serial numbers and firearm manufacturer’s information are important and must be more than just “present and eye-readable.”

Located in between the BATFE-required serial number and name of the manufacturer and model, the 2D Matrix Code is readable by internal tracking machines at the Remington plant. The code isn’t required by law and is used to track serialized parts through the assembly process.
Located in between the BATFE-required serial number and name of the manufacturer and model, the 2D Matrix Code is readable by internal tracking machines at the Remington plant. The code isn’t required by law and is used to track serialized parts through the assembly process.

According to Bureau of Alcohol, Tobacco, Firearms, and Explosives (BATFE), firearm serial numbers must meet the following requirements:

  • Must be conspicuously engraved, cast, or stamped (impressed) on the firearm frame or receiver.
  • The serial number cannot duplicate the serial number appearing on any other firearm the importer previously imported.
  • For firearms imported after January 30, 2002, the engraving, casting or stamping (impressing) of the serial number must be to a minimum depth of .003 inch and in a print size no smaller than 1/16 inch.

Markings must also include the name of the manufacturer, the firearm’s country of origin, model designation (if assigned), caliber or gauge, name of the importer, and the city and state of the importer. Interestingly, if a foreign manufacturer didn’t mark their firearms to this standard, the importer must do so within 15 days of their release from Customs and Border Patrol Custody.

Section 478.2 (a)(1)(i) also specifies: By engraving, casting, stamping (impressing), or otherwise conspicuously placing or causing to be engraved, cast, stamped (impressed,) or placed on the frame or receiver thereof an individual serial number. The serial number must be placed in a manner not susceptible to being readily obliterated, altered, or removed …
That’s no small amount of information, but what does that have to do with the unsightly square of dots?

The Illegible And Offensive 2D Matrix Code

At the risk of allowing the loud voices of a few speak for the majority’s opinion, most of the commenting firearm forum enthusiasts found the square of dots, the 2D Matrix Code mark, well … ugly. At a minimum, most found the mark as cosmetically welcome as Ike Turner at a NOW convention, not to mention the object of several government conspiracy theories.

The Standard Manufacturing DP-12 shotgun is one of the rare exceptions with a QR Code to access the owner’s manual. Unlike the 2D Matrix, this mark has some value for the end-user, but isn’t used in the manufacturing process.
The Standard Manufacturing DP-12 shotgun is one of the rare exceptions with a QR Code to access the owner’s manual. Unlike the 2D Matrix, this mark has some value for the end-user, but isn’t used in the manufacturing process.

Both the numbers and letters made from a line of dots, and the squares of asymmetrical dots, are designed to be read by a machine—usually with a laser inside a tooling machine or the handheld device of a factory line technician. The marks allow manufacturers to read and track a serialized part through the assembly process and into an integrated order tracking system. The parts, and ultimately the assembled firearm, can then be located anywhere on the factory premises during production and electronically logged to a specific customer when shipped.

So, if the BATFE requires this information and it must be visually legible, why do manufacturers also need an ugly mark so a machine can read it? The simple answers are efficiency and liability. In addition to production tracking, manufacturers can also ensure serial numbers are neither omitted from a series (requiring the manufacturer to account for a gun never made) or duplication (stamping two guns with the same serial number). Sorry, collectors.

Again, the 2D Matrix Code is simply a machine-readable image able to store much more information per square inch than a series of dots shaped like numbers or letters. They’re not readable by common devices such as your smartphone like Quick Response (QR) Codes and have no value to the end consumer.

However, the marks are regulated for industrial quality and consistency standards by AIM, the Association for Automatic Identification and Mobility. The exact information contained in a specific 2D Matrix Code mark is proprietary to each firearm manufacturer. So, you’d have to get the manufacturer to agree to have their machine read your mark and then share what it says.

Epidemic Or Pandemic?

Are the 2D Matrix Codes a COVID-like global pandemic for firearm aesthetics, or are they more akin a regionalized malaria epidemic. The answer is the latter. The BATFE doesn’t require manufacturers to use an electronically readable marking device, a 2D Matrix Code, nor an integrated part tracking system. Smaller manufacturers would have to reach a scale where replacing people with machines is economically sensible. In other words, if you make millions of guns a year, the investment makes sense. If you’re a small custom shop, it’s unlikely.

The 2D Matrix and QR Codes differ in appearance and use. The 2D Matrix (left) can be identified by the straight lines along the bottom and left sides. The QR Code (right) has three squares at the corners. Smartphone apps can scan the QR Code to link to websites or documents.
The 2D Matrix and QR Codes differ in appearance and use. The 2D Matrix (left) can be identified by the straight lines along the bottom and left sides. The QR Code (right) has three squares at the corners. Smartphone apps can scan the QR Code to link to websites or documents.

In silent acknowledgment of this electronically induced wart, some manufacturers managed to nest their 2D Matrix Code in less obvious locations, such as under a pistol slide. Still, most production line machines need the marks to be external and visible in order to read and track a part.

Not A QR Code

I’ve no doubt some shooters will try it, but 2D Matrix Codes aren’t designed to be scanned for information relevant to the owner or open an internet page via a scanning app on your smartphone. That’s what a QR Code does.

Visually, you can tell a 2D Matrix Code from a QR Code as the latter will have three large squares in the corners in addition to the array of dots or squares. The 2D Matrix Code will have solid lines at the left and bottom of the mark and no squares in the corners. Also, neither 2D Matrix Code nor QR Codes are the same as the more familiar bar codes that come on consumer packaging. So, for God’s sake, don’t attempt to scan your pistol at the grocery store checkout.

However, some airsoft and air rifle companies have added QR Codes to their rifles along with the serial numbers, often on a decal, as they’re not bound by ATF marking standards. In one exceptional case, the Standard Manufacturing DP-12 pump shotgun uses a QR Code on the synthetic stock to reference a website for its user’s manual. The QR Code is a clever, techie addition and not out of keeping with the shotgun’s futuristic aesthetic design of the shotgun. However, it’s not to be confused with the 2D Matrix Code, nor would it satisfy BATFE requirements.

So, love them or hate them, that’s what’s showing up on some of your new firearms. You can remove your tinfoil hats; there’s no secret chip in the gun, GPS locator, or biometric scanner—at least not yet.

Editor's Note: This article originally appeared in the October 2020 issue of Gun Digest the Magazine.


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Gun Oil: What Modern Guns Require To Fight Friction

Does your gun oil bring out the best in your firearms?

When was the last time you gave as much attention to your gun oil as your ammunition, magazines, optics or lights? Because lube can’t attach to a Picatinny rail, get laser-etched or dipped in the latest absolute invisibility camo pattern, probably very little.

When was the last time you considered what’s in your lubricant and how that impacts the performance of your firearm? Probably the same answer.

100-Year-Old Lubricant

Sadly, many American firearm owners lubricate their guns with “what they’ve always used” and live with its shortcomings. In fact, the top-selling gun oil in the United States was introduced in 1913—before World War I! It was designed first and foremost to prevent rust; lubrication was a distant second, and cleaning only happened with aggressive scraping and additional harsh chemicals.

Used more broadly today than at any time in history, a suppressor’s downsides comprise the extra gases and heat channeled back through the action. How does your typical lubricant hold up when you’re running a can?
Used more broadly today than at any time in history, a suppressor’s downsides comprise the extra gases and heat channeled back through the action. How does your typical lubricant hold up when you’re running a can?

However, this historical “blindness” isn’t without cause: Until the end of the 20th century, the single greatest enemy to carbon-steel and wood firearms was rust. The cleaning process for firearms of this era required harsh chemicals and often hours of scraping that put excessive wear on internal components. But, it had to be done: Rust was every gun’s “public enemy number one.”

Worse, neither the firearm’s function nor its reliability was materially improved by this method or lubrication. Not only were gun owners fighting a losing war against the ravages of rust, but also against heat, friction and chemistry.

Modern Performance and Reliability Enemies

Today, rust isn’t the threat it once was. Most modern firearms are made from a combination of synthetic materials, stainless steel or coated metals. But, along with modern materials come gas-operated designs with smaller, faster-moving parts and tight tolerances. Today, friction, heat and compounded contamination are the modern enemies to reliability and performance.

Why? The same gases used to propel the bullets and cycle actions carry contaminants around—and into—every angle and crevice of your firearm. Driven by heat and pressure, these gases bake layer after layer of carbon onto moving parts and into gas ports. Eventually, the layers build up and change the parts’ geometry. The contaminated parts can no longer move within or past one another, and function slows … or ceases outright.

For the modern firearm powered by its own gases, staying lubricated under heat, pressure and friction—and fighting carbon buildup—is critical. More importantly, how quickly can you remove the unavoidable contamination from the parts and get your AR reliably back into action?
For the modern firearm powered by its own gases, staying lubricated under heat, pressure and friction—and fighting carbon buildup—is critical. More importantly, how quickly can you remove the unavoidable contamination from the parts and get your AR reliably back into action?

The historical solution, often sold as a “character-builder” by generations of drill sergeants, is to scrape parts with metal tools, chemicals, picks and brushes to remove every visible fragment of carbon. This approach damages the parts with each cleaning, often to the point of failure—or, if an armorer is lucky, deemed “out of spec”—and replaced.

This self-defeating process is separate from the excessive time wasted for such a laborious process that just about any reasonable person would rather spend doing something else … such as shooting.

So, if modern firearms require a different lubricant solution to support their unique functional requirements and materials, what should it contain?

  • A high-quality synthetic lubricant base capable of enduring the high heat and pressures of modern firearms without breaking down, being displaced by water or gelling in low temperatures, along with a rust-prevention additive.
  • A penetrant to reach the micro-crevices between small parts that can become clogged with contamination.
  • A detergent to clean the moving parts and bearing surfaces while the weapon functions, yet is still safe on synthetic materials and finishes.
  • A dispersant to prevent the contamination from re-adhering to the metal, particularly under heat and pressure.

Functionally, a modern gun oil should also speed cleaning and lengthen the amount of time between required cleanings. This element is particularly important if you’re serving in an austere environment in which a reliably functioning firearm could determine your ability to defend yourself from harm.

Today, while rust is a factor any quality lubricant should inhibit, the contamination buildup in the bolt carrier group can change the geometry of the parts and lead to failure. 
Today, while rust is a factor any quality lubricant should inhibit, the contamination buildup in the bolt carrier group can change the geometry of the parts and lead to failure. 

Ask yourself: If you had two identical firearms you carried and utilized daily, wouldn’t the more reliable of the two be the one with a lubricant that functioned consistently and for more extended periods under heavy use, yet was easier to clean? Viewed in a military context, isn’t the ability to stay in the fight longer and be cleaned quickly also a significant tactical advantage?

Modern Gun Oil

One recent entrant to the market—born on a poncho at Fort Benning, Georgia, amidst an array of AR parts, picks, brushes, patches and issued chemicals—might’ve cracked the code.

Created with modern firearms and their needs in mind, EDC-CLP’s patented chemical components not only continue to clean and lubricate for extended periods under excessive heat and pressure, they also reach into the micro-crevices contaminated with baked-on carbon that picks and brushes cannot reach.

One key addition to the formulation is a “high-pressure additive” with positively charged molecules that adhere to the metal. In other words: It keeps the product in and on the parts—cleaning and lubricating—during use, rather than being forced off by friction and gases. The high-pressure additive also provides the added benefit of suspending the contamination in the lubricant that the dispersant and detergent elements slough loose from the parts.

Gun oil 3

How does it perform outside the chemistry lab?

EDC-CLP’s positive impact on your gun’s function is both immediate and gradual. After a single application, a user will feel an instant improvement in lubricity (slipperiness). In most cases, follow-up cleaning requires little more than a wipe-down and reapplication.

EDC-CLP doesn’t require special preparation of the weapon’s parts in a sterile environment in order to work. It can be applied on top of existing gun oils or lubricants if necessary.

So, ask yourself, Which “war” is your lubricant fighting?

For more information on ELC-CLP Lubricant, please visit edcclp.com.

Editor's Note: This article originally appeared in the 2021 Long-Range Shooting issue of Gun Digest the Magazine.

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AR-15 Maintenance: Upgrading Your Bolt And Bolt Carrier Group

AR-15 maintenance doesn’t have to be expensive. A quick update to the bolt can breathe new life into your go-to gun.

Why you should pay attention to the bolt and BCG with your AR-15 maintenance:

  • Relatively inexpensive upgrade
  • Only takes minutes to replace parts
  • Eliminates most common failure — failure to extract
  • Bolt and BCG ware quickly giving exposure to heat, friction and contamination

When it comes to guns, it seems there’s always something on the horizon newer, lighter, faster, made from an exotic metal — or even just a different color. Sometimes the changes are innovative, and sometimes it’s just marketing hype. Either way, new features and their new price tags often mean more money that might be better spent on practice ammo or killing a credit card bill.

AR 15 Maintenance 6
But for those of us who take our personal safety seriously and are mindful of the importance of a well-maintained firearm, a few simple checks and a change-out of inexpensive replacement parts in your bolt can keep your AR running reliably — and prevent one of the most common stoppage issues experienced by AR shooters: a failure to extract.

Just so we’re on the same page, the plain meaning of the term “failure to extract” is when the spent cartridge casing will not properly exit the rifle upon firing. Simple enough to identify. A combination of factors can create this problem, but the causes — other than a dirty action and an out-of-spec magazine — are most commonly an issue with the extractor, extraction process or gas system.

Read Also: Addressing Common AR Malfunctions

Either the extractor — a hook-shaped, spring-tensioned part located on the front of the bolt at approximately the 10 o’clock position as viewed from the bolt face — is failing to grab the rim of the casing and pull it from the chamber, or the gas system isn’t supplying the force necessary to enable the bolt to cycle.

The extractor is actually part of the AR’s bolt head, and when installed it has a locking lug on the outside and a round, claw interior that completes the circle of the bolt face. The extractor sits opposite the ejector pin, and the two parts work in tandem, with the extractor anchoring the base of the cartridge case and the and ejector pin pushing the opposite side to send the spent case out of the action when the weapon cycles.


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The bolt carriage group in general, and the bolt, specifically, are exposed to a great deal of heat, friction and contamination. Each time a round fires, this system of parts experiences forceful movement, friction and spring compression, as well as linear and rotational forces. Like any machine, the parts wear with use. In particular, the springs are repeatedly compressed and the metal parts heat and cool. The inevitable results are the springs get weaker and eventually provide resistance beneath their manufacturer’s specifications, and metal parts can chip, shear or shatter.

Read Also: A Word on AR-15 Carrier Life

Like brakes on our vehicle, heading downhill into a traffic pile-up is not the time to consider the last time you replaced worn parts. The good news for you and your AR is that a simple and inexpensive upgrade exists that takes only minutes and a few dollars to complete.

The Extractor And Extractor Spring

My preference for bolt maintenance is the Bravo Company Manufacturing (BCM) SOPMOD Bolt Upgrade/Rebuilt Kit. The kit may be purchased in two ways: The basic package is an Extractor Spring Upgrade Kit that includes the extractor spring, extractor insert and Crane Industrial mil-spec O-ring — with a miniscule MSRP of $4.95. The full Bolt Upgrade/Rebuild Kit also includes the Extractor Spring Kit along with a BCM extractor, an extractor pin and three USGI gas rings for only $29.95.

Read Also: How To Care For And Upgrade AR Springs

I prefer the BCM kit; I have first-hand experience with the obsessive quality control Paul Buffoni and the BCM team puts into their parts. BCM’s high standards for specifications and tolerances have the reputation of the highest OEM part reject rate in the industry. My first and favorite AR is a BCM, and after more than 12,000 rounds with minimal issues, I finally conceded to follow my own advice and give the bolt a rebuild. After thousands of rounds, ammo types, external conditions and heavy use, it was still as reliable as the day it came out of the box.

The extractor is a critical element to the proper functioning of the AR’s gas impingement system. Its function is to grab the base of the cartridge casing and mechanically escort it into and out of the AR’s action during the firing sequence.
The extractor is a critical element to the proper functioning of the AR’s gas impingement system. Its function is to grab the base of the cartridge casing and mechanically escort it into and out of the AR’s action during the firing sequence.

But nothing lasts forever.

Having started with a BCM, I was replacing an old part with a new one of the same quality. But for those who are not sure of the provenance of their ARs parts, installing a shot-peened USGI spec extractor is likely a step-up in quality and reliability, given the standards some manufacturers tolerate. Additionally, the extractor spring is chrome silicon, heat treated, stress-relieved and shot-peened, which means it’s made of the best components available and manufactured such that it will continue to perform long after lesser components fail.

The change-out requires only a punch to push out the extractor pin, a quick clean of the bolt’s surface beneath the extractor and replacement of the new spring and extractor insert in the same manner they came out. Note the orientation and thickness of the spring relative to the bolt, and be certain to replace the two parts in the same order. Press and hold the extractor in place and replace the pin.

When working with a new spring, it might take more pressure to line up the extractor with the holes in the bolt, but just take your time. Upon inspection, my extractor claw showed minimal wear for the number of rounds cycled through the AR. It by no means looked new, but it was far better than other sad examples I’ve seen where the claw is worn to a humble nub, or where the claw actually snapped off — which is a catastrophic failure.

I have omitted mentioning the mil-spec O-ring because many consider it superfluous and an early fix to a design flaw in the extraction timing. The historical arguments are many, but the ultimate answer is that it’s optional with modern extractor springs, so decide for yourself — or try it both ways and see which works better for your AR. It’s unlikely that you’ll notice a difference.

The Gas Rings

The second element of the bolt rebuild is a replacement of the three gas rings on the tail-end of the bolt. The rings modulate the amount of gas that passes through the bolt carriage group and form a seal that pushes the bolt forward as part of the firing sequence.

Do you need the newest flashy add-on, or would your time and money be better spent on ensuring your AR functions reliably? The author’s go-to AR had functioned well through 12,000 rounds of hard use, but it got a bolt upgrade that include a new extractor to reduce the likelihood of stoppages and keep the rifle healthy — all for less than $30 bucks.
Do you need the newest flashy add-on, or would your time and money be better spent on ensuring your AR functions reliably? The author’s go-to AR had functioned well through 12,000 rounds of hard use, but it got a bolt upgrade that include a new extractor to reduce the likelihood of stoppages and keep the rifle healthy — all for less than $30 bucks.

Some shooters argue that an AR will function without these rings, and they may be correct. But purposely or negligently creating gas imbalances in your ARs system where reliability is your primary concern is a silly idea, so treat the gas rings as maintenance items and replace them regularly. A BCM ring three-pack will cost you $2.95 — so, other than a good cleaning, it’s the least expensive way to improve the reliability of your AR.

Read Also: Under Gassed? Check Your Gas Rings

A practical but unscientific test is to press the bolt into the carrier, hold the bolt carrier group (BCG) in the air by the bolt and observe whether it slides down. The opposite approach works by pulling the bolt out and setting the BCG on the bolt head: If the bolt can hold the carrier in either direction, your rings are still in good shape. The rule of thumb is to change them out every 5,000 rounds. Again, my rifle was at 12,000 rounds and the rings passed the test, but I changed them out anyway.

Removing the O-ring is most easily accomplished with the help of a dental pick to spread the ring at its respective split and slide it off the body of the bolt. The first ring is tricky; the second and third are easy. Install the new rings by sliding them down over the tail of the bolt making sure they don’t overlap.

Back In Action

I put the AR to work the next day in a two-day carbine course with Kyle Defoor’s Proformance Shooting. Through 600 rounds of Black Hills Ammunition 77-grain OTM between two shooters, we experienced zero fails, just like before, along with the added confidence that a potential extraction problem was further away.

All in, the most expensive approach to this maintenance exercise was less than $30, but you can still improve your system by choosing the gas rings or extractor springs, both of which are less than $5. The entire rebuild process took about 15 minutes.

The extractor sits at the 10 o’clock position on the bolt (shown here removed). It has a lug on the outside, and a round claw on the inside that completes the circular bolt face.
The extractor sits at the 10 o’clock position on the bolt (shown here removed). It has a lug on the outside, and a round claw on the inside that completes the circular bolt face.

If this process sounds complicated but you’re still concerned about your bolt’s maintenance, a brand new bolt from BCM is $79.95. Additionally, if your existing bolt functions normally and you choose to replace it as a matter of maintenance, keep it as a backup.

In many of today’s aftermarket pistol grips, there’s a locking cover that turns the hollow grip into a small storage compartment, and most will accommodate a bolt. Give it a light lube and wrap it in a small Ziploc bag to waterproof it and keep it quiet, and a back-up will never be far away.

Editor's Note: This article originally appeared in the December 2018 issue of Gun Digest the Magazine.

Big-Bore AR Evolution Is Larger Than Life

The big-bore AR continues to evolve, bringing heavier loads and practical options to the modern sporting rifle.

How Top Big Bore AR Options Mesure Up:

Ignoring for the moment that AR acronym stands for “Armalite Rifle” rather than “assault rifle,” the AR platform continues to evolve in functionality and efficiency, all the while fending off potential bans and misinformation. But let’s get down to the basics that have made Eugene Stoner’s design so long-lived.

Big Bore AR 10

First, the ergonomics are universally appreciated. When viewed broadly over its 55-year lifespan, little has changed in terms of the pistol grip locations and angle, the trigger and safety location, the upper/lower concept, and the mechanism for loading and re-loading. The bolt carriage group (BCG) design remains largely the same, as does the direct impingement system that utilizes gas and a buffer spring to cycle the rifle’s action. Have there been improvements in handguards, stocks, charging handles, optics and triggers? Certainly. Still, the fundamental platform remains the same.

So what’s next? The military side of the house has bolted on and integrated optics, electronics and ergonomic improvements designed to improve reliability, range and accuracy in their issued calibers. With the ongoing war on terror pushing 20 years, we sadly have buckets of trial and error cycles to refine what works on the outside of the weapon system.

But what about the inside of the rifle and the civilian market? For hunters, target shooters and general enthusiasts, finding applications for the AR platform has taken a slightly different path. At times, such as the .300 Blackout/Whisper, the cross-over had its genesis in the military world — but in many cases, American civilian shooters began doing what they do best: tinkering with an existing idea and adapting it to new applications.

Bring On The Big Bores?

Ironically, the concept of a “big bore” in the modern sporting rifle vernacular has come to mean anything larger than the 5.56x45mm NATO round issued for the M-16/M4 platform since its introduction into military service in the 1960s. However, Stoner’s original design, the AR-10, was chambered for the 7.62x54mm (.308 Win.) cartridge. The issued rifle of the day was the M-14, and the prevailing military thinking was that a .30-caliber bullet was the optimal balance between weight, range, and knockdown power.

Big Bore AR 11

In a Cold War departure from the experiences of World War II and Korea, the decision was made to reduce the cartridge to the current 5.56x45mm. Nonetheless, Stoner’s internal design did provide several scalable advantages for larger calibers.

First, the buffer spring and gas direct impingement system considerably reduces felt recoil by utilizing a buffer tube and spring to absorb the kinetic energy displaced backward when a cartridge fires. Second, it also eliminates the need for an operating rod, which increased the weight and mass moving toward the shooter when a round cycled. AK fans will note this system diminishes reliability and makes for a dirtier action, and they’d be right. But until we’re shooting “freaking laser beams,” the laws of physics still apply, and you have to give to get.

More Info: Five Top Big-Bore ARs and Cartridges

So with the pluses and minuses acknowledged, let’s dig into the new stuff. Like rocket ships and dragsters, Americans aren’t historically burdened by practicality when it comes to pushing the engineering envelope of speed and power. ARs are no exception, and the direction within the civilian market has been to adapt the platform to larger calibers typically reserved for bolt or lever-action hunting rifles. We love our speed, but the sheer kinetic punch of a .40 caliber or larger rifle bullet seems to be in our DNA.

The Wilson Combat .458 Ham’r

Since 1977, Wilson Combat (WC) has been finding ways to make the old better or come up new twists on time-tested themes. Few, if any, 1911 aficionados don’t count their collection incomplete if there is not a WC square gun in it.

The chamber of a Wilson Combat .458 Ham’r launches a bullet up to 400 grains at more than 2,000 fps, delivering a devastating 3,000 ft-lbs. of energy.
The chamber of a Wilson Combat .458 Ham’r launches a bullet up to 400 grains at more than 2,000 fps, delivering a devastating 3,000 ft-lbs. of energy.

In 2016, both Bill Wilson and his grandson took a Cape buffalo on a trip to Africa with a .458 SOCOM. In both cases, and on smaller, “less-dangerous” game, it was also effective. Also, in some circumstances at longer ranges, the bullets didn’t fully expand, but the energy and size of the projectile closed the terminal ballistic game. Despite the relative success in the field, it sparked an idea in Bill’s mind that the .458 cartridge could use some help.

At a muzzle velocity of about 1,900 fps for a 300-grain round, the .458 SOCOM’s ballistics are similar to the classic .45-70 Gov’t. But like the .45-70, the trajectory graphs like a rainbow, making holdover a challenge at longer ranges. In other words, every little bit of speed helps.

The .458 Ham’r, with the same Barnes round, rips out at 2,100 fps and nearly 3,000 ft-lbs. of energy from the muzzle. This not only improves terminal performance, but it also mitigates the margin of error if the shooter is using open or red-dot sights and must visually estimate both distance and holdover.

Building the .458 Ham’r was not all about the cartridge, however. Wilson wanted to eliminate some of the reliability symptoms he had occasionally seen with the .458 SOCOM. Built on an AR-10 upper, the system can handle the increased chamber pressures of up to 46,000 psi, and Wilson shortened the bolt carriage group by ¾-inch to better handle the shorter cartridge. Other small tweaks, such as a larger ejection port to accommodate the wider case and a switch to a rifle primer for their WC’s proprietary ammo, further tightened the reliability and accuracy sweet spot.

Read More: The Big Shot — Wilson Combat’s .458 HAM’R

The lower for the .458 Ham’r is specific to the rifle’s unique design, so they only sell complete rifle packages, but WC does offer a .458 SOCOM upper for AR lowers.

The .450 Bushmaster

Many would rightly argue the .450 Bushmaster began the big-bore AR movement. Originally conceived by Tim LeGendre as an answer to Colonel Jeff Cooper’s disappointment in the 5.56x45mm (AR-15’s) terminal effectiveness on game, Cooper wanted a “thumper” that could be counted on to consistently put game on the ground inside 200 yards. After some experimentation and a joint experiment with Hornady Ammunition, Bushmaster launched the 250-grain SST Flex-Tipped .45-caliber cartridge in a straight-walled .284 Winchester case and dubbed it the .450 Bushmaster.

The .450 Bushmaster entered the big-bore AR trend early, and offers a relatively flat trajectory inside 200 yards.
The .450 Bushmaster entered the big-bore AR trend early, and offers a relatively flat trajectory inside 200 yards.

The advantage to this cartridge within the AR platform had several benefits. First, it lent itself to a single-stack, magazine-fed operation, exceeding that of most internally fed bolt-action rifles. Further, the muzzle velocity of 2,214 fps (in the 250-grain bullet) provided a relatively flat trajectory inside of 200 yards. Finally, the 2,700 ft-lbs. of energy delivered a significant terminal punch, along with the wide frontal profile (vs. a .30 caliber).

The round grew in popularity with the increase in the number of feral hogs nationwide and made for an excellent deer rifle. Most notably, the .450 Bushmaster uppers are compatible with most AR-15 lowers, which allows budget-minded shooters to simply purchase the upper, ammo and new magazines to create a dramatically different hunting platform vs. their 5.56x45mm/.223 Rem.

Bushmaster Arms produces the .450 Bushmaster AR in a 16- and 20-inch barrel models. For 2017, they rolled out a SOPMOD stock, ALG Defense nickel Teflon, mil-spec trigger, a square key drop modular hand guard and a slightly enlarged ejection port.


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The Bushmaster .450 has also enjoyed increasing popularity due to regulation changes in some states where straight-wall-cased cartridges are allowed where hunters were previously limited to shotgun slugs-only (non-rifles). Be sure to confirm in both your state and region whether regulations allow for straight-walled rifle cartridges and, if so, the capacity limits. Game wardens tend to be universally intolerant of hunter’s pleading ignorance on this point.

The Alexander Arms .50 Beowulf

Taking the big-bore concept and making it slightly bigger, Bill Alexander of Alexander Arms introduced the .50 caliber Beowulf in 2001. Alexander has been out in front of several trends that continue to grow in popularity, such as the 6.5mm bullet which he chambered for the AR-15 platform in the 6.5 Grendel in 2001. In a nod to his British heritage, Beowulf and Grendel are characters (both heroic and evil) from one of the oldest surviving pieces of English literature.

The Alexander Arms .50 Beowulf, as compared to the .223 Rem. of an AR-15, has up to seven times the bullet mass, three times the energy and an average of twice the frontal area.
The Alexander Arms .50 Beowulf, as compared to the .223 Rem. of an AR-15, has up to seven times the bullet mass, three times the energy and an average of twice the frontal area.

Beowulf, a monster and dragon-slayer even into his old age and the subject of the ancient epic poem, is a fitting name for the cartridge that ranges in mass from 200 up to 400 grains. The muzzle velocity varies between 1,771 and 1,870 fps depending upon the load. Like the .450 Bushmaster, the .50 Beowulf upper can be purchased instead of a complete rifle and bolted to a mil-spec AR-15 lower.

The .50 Beowulf’s advantages, like the other big bores running in an AR platform, are best illustrated by a comparison with the standard issue 55-grain .223 Rem. bullet. The .50 Beowulf has four to seven times the bullet mass (depending on the load), three times the energy, and on average twice the frontal area.

Also See: Alexander Arms .50 Beowulf Hunter

Granted, it moves slower and has less range, but to broad-brush this comparison in football terms, imagine you’re a quarterback. Would you rather be sacked by a single safety … or a linebacker, defensive end and a nose guard all at once? The relative effect is similar on game with a 200-yard range: The .50 Beowulf delivers a blow that neutralizes most earthly mammal’s desire to do anything but go down and stay down. Alexander Arms has also recently released a 200-grain cartridge with an advertised muzzle velocity of 2,500 fps.

Innovation Or Hype?

Ultimately, a big bore AR is a personal choice. There are definitely longer range bolt-action rifles on the market and very solid AR offerings in the .260-.30 caliber range that cost more than your truck — and whose ballistics may, in some respects (particularly distance), outperform these big bores. But if your big game quarry is typically taken within 200 yards, these AR’s will save you the trouble of tracking if your shot is well placed — their terminal impact is simply devastating. Or, if you’re a range guy and like to make things explode when you shoot them, big bore ARs are definitely for you and a helluva lot of fun.

AR-Big-Bore

Finally, if you’re an average Joe with kids to feed who wants to have an interchangeable mil-spec AR and a heavier hunting option without breaking the bank, a big bore AR upper is often a solid, more-affordable option than a second gun.

Editor's Note: This article originally appeared in the October 2018 issue of Gun Digest the Magazine.

Best Ballistic Calculators For Improved Long-Range Shooting

Calculations that once took a room filled with computers can now be completed in seconds on your smartphone via a first-rate ballistic calculator.

What are the best ballistic apps:

Like so many things in our modern lives, precision shooting solutions have found their way onto our smartphones. Ballistic calculators or “solvers” have evolved and miniaturized from large computers to handheld devices — and now into smartphone apps. But are the phone apps any good? And if they are, what does the average shooter get from spending money to purchase one and investing the time to learn the systems?

Accurate muzzle velocity measurements specific to your rifle and your load are critical inputs to enable the calculators to function correctly. The Magneto Speed chronograph mounts to the muzzle, or the suppressor in this case, to measure the velocity of the bullet as it exits the rifle.
Accurate muzzle velocity measurements specific to your rifle and your load are critical inputs to enable the calculators to function correctly. The Magneto Speed chronograph mounts to the muzzle, or the suppressor in this case, to measure the velocity of the bullet as it exits the rifle.

The good news is that the cost of a smartphone-based ballistic calculator ranges from free to $29.99. For the average shooter, a free app can considerably improve his or her ability to accurately engage targets and, more importantly, learn the consistency and limitations of a rifle and load combination. And because none of them are overly expensive, you can download several and pick one you like best from the crowd.

As for investing time, the complex math is handled behind the digital curtain, and the inputs are typically the familiar rolling tumbler interfaces to select settings or blank fields to type in data. But before you go thinking you’re about to become a 1,000-yard long-range ninja, there are a few things to keep in mind about what a ballistic calculator will — or will not — do for you.

How will a ballistic calculator help my shooting?

Aside from the inherent attraction of knowing how one’s bullet flies through space (we’re gun nerds, after all), a ballistic calculator tells you where your bullet will strike a target at given distances, under pre-defined conditions. The forces of gravity, wind and your cartridge’s load and projectile behave in a mathematically predictable but sometimes non-linear manner as the bullet flies through super-sonic, trans-sonic and sub-sonic speeds.

These changes, and the required aiming adjustments along with a vast library of load and projectile data, are the reasons to own a solver. But does all this technology and math matter? It depends. If you’re a whitetail deer hunter who rarely takes shots outside 100 yards in a dense forest, then no — much of this data will not help you. The shorter the distance to the target, the less impact external forces have on a projectile, so your time and money would be better spent practicing good form in multiple shooting positions using a consistent load appropriate to your quarry. If you’re into long-range target shooting as a discipline or hunt in areas where longer shots are ethically more frequent, a solver can be a profoundly useful tool, and you should take the time to master its functions.

This diagram shows the “Four Degrees of Freedom” the Hornady 4DOF calculator measures to predict the path of the projectile. Note the “Angle of Attack,” which is the added variable in addition to windage, elevation and range.
This diagram shows the “Four Degrees of Freedom” the Hornady 4DOF calculator measures to predict the path of the projectile. Note the “Angle of Attack,” which is the added variable in addition to windage, elevation and range.

GIGO: Garbage In = Garbage Out

Like any computer program or math problem, the results are only as good as the inputs. In other words, if you’re using incorrect rifle and load-specific data, the solutions any solver spits out will be equally and sometimes exponentially incorrect.

The key data points you should be able to collect are:

  • Muzzle Velocity: How fast the bullet is moving when it exits the rifle.
  • Cartridge Load: The caliber, projectile shape and powder charge.
  • Atmospherics: Temperature, altitude, barometric pressure, etc.

Muzzle velocity is arguably the most critical input variable in calculating the downrange performance of a particular round. Keep in mind that there are variances in every cartridge created by differences in powder charge, thickness of the brass wall, seating depth and a multitude of other factors. Talk to any handloader and they’ll opine endlessly as to which of these factors matter most and when, but the bottom line is that in both handloaded and factory ammo, variations from one round to the next will inevitably occur. This translates to different speeds at which a projectile exits the rifle’s muzzle, and therefore how far the bullet will travel during a fixed period of time (i.e., 1 second).

A good rule-of-thumb is to take the average of at least five rounds. Most shooting ranges will have chronographs for rent or a rangemaster who will chrono your rifle for a fee. I prefer a MagnetoSpeed barrel-mounted chronograph because there is no device to shoot through (as with a chronograph on a stand) or get blown over in the wind, nor do you have to call a range halt to walk a traditional chronograph in front of the firing line.


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Use your instincts: If the measurements vary wildly, start over and compare the averages of several five-shot groups if necessary. So much of the ballistic math depends on this single data point that it’s worth your time to get as accurate a number as possible. Muzzle velocity is an average, and like many other calculations the solvers will make, some assumptions and rounding will occur, so where you can control the inputs you need to make them as perfect as possible.

If you’re not a handloader, use cartridges from the same box and lot whenever possible because factory conditions can vary from day-to-day. Always avoid different brands and bullet weights. What you’re trying to establish is a baseline for a single load (powder charge) in a particular rifle of a specific bullet (full metal jacket, open-tip match, soft-tip hunting round, etc.).

Regardless of which ballistic calculator you choose to employ, the “garbage in, garbage out” mantra applies: The information you get from that app is only as good as the information you give it to work with.
Regardless of which ballistic calculator you choose to employ, the “garbage in, garbage out” mantra applies: The information you get from that app is only as good as the information you give it to work with.

Again, there’s a multitude of smaller factors that can affect performance, such as heat and cleanliness of the barrel, but knowing the mass of the projectile flying through the air, and that it’s the same from shot to shot, is critical. Throwing together several projectile weights and brands will give you inconsistent data, skew your results and ultimately waste your time.

It’s important to note the factory velocities and bullet drop tables on the side of the box will almost never match your rifle. The box data does not tell you the length of the barrel through which the bullet travelled, the atmospheric conditions when the round was fired or how many shots were tested. It’s an approximation, and one you can use if you must — but where possible, collect the data yourself.

For example, the factory might have used a 24-inch barrel to log the velocity data. Your rifle might have a 22-inch barrel, which will likely reflect lower velocity (generally, shorter barrels see a reduced velocity, all else being equal). Inputting the higher velocity number from the box will skew the calculations. It’s also worth noting that some solvers will have functions that allow you to back into a rifle-specific velocity by using the factory numbers and adjusting for barrel length, but this will never be as accurate as data collected yourself.

Atmospherics — the external conditions such as temperature, humidity, barometric pressure and altitude — will all affect how a projective flies through space over distance. Some solvers can download real-time weather data into their calculations. This feature is convenient, but keep in mind the data will likely come from the nearest weather station that might be miles away and at a different altitude. The best method is to have a local meter such as a Kestrel 5700 or similar device. If neither of these are available, many public ranges will know the specific altitude of the range and have a thermometer and barometer mounted for the shooters. If you don’t see one, ask the rangemaster or other shooters if they know … someone likely will.

Download Away

Presuming you have a consistent rifle setup with good glass that allows for repeatable adjustments that reflect the windage and elevation adjustments the ballistic calculator will derive, here are a few apps to consider. Given that several are free, download them all and compare the results and ease of use and use the one you prefer.

I’ve used all of the listed calculators to a greater or lesser degree, and each has performed consistently. How each solver uniquely calculates trajectory is beyond the scope of this piece, but these are all solid options, and each allows for “trueing” a rifle to create ballistics tables to adjust for how a round performs in a particular rifle vs. how the math says it should.


4 DOF (Four Degrees Of Freedom)

Ballistic-Calculator-9Developer: Hornady Manufacturing
Price: Free

Hornady went back to the drawing board and used Doppler radar to measure (in addition to the standard windage, elevation and range inputs) bullet trajectories to include a fourth factor: the angle of attack. This method takes into account the angle of the bullet’s launch from horizontal, which can have an impact on its flight. Hornady also departed from the traditional ballistic coefficient (BC) measurement of the efficiency with which a bullet flies through the air, and instead they used a drag coefficient (CD) vs. Mach value. Hornady feels this system reflects a more accurate representation of a bullet’s flight, but the program can also utilize BC values to calculate tables for projectiles upon which they have not collected data. It can also communicate via Bluetooth with other external devices.


Shooter

Ballistic-Calculator-2Developer: Kennedy Development Group, LLC
Price: $9.99

The Shooter app’s greatest strength is its simplicity. It’s simple, fast and easy to use. In addition to having a built-in library of more than 1,300 bullets, it also has G7 BC data collected by engineer and ballistician Bryan Litz, and it can interface with atmospheric data collected by Bluetooth enabled Kestrel devices.

 

 

 

 

 

 


Lapua Ballistics

Ballistic-Calculator-3Developer: Nammo Lapua Oy
Price: Free

Lapua Ballistics took the four degrees of freedom and Doppler radar concept two steps further and added the impact of the rotational movement on the elevation and range axis to derive an even more precise prediction of a bullet’s flight over time and through space. The only drawback of this system is it only includes Lapua’s projectiles.

 

 

 

 

 


BulletFlight M

Ballistic AE 3D Trajectory Imagin (1)Developer: Runaway Technologies, Inc
Price: $29.99

The “M” version of BulletFlight is the most expensive offering in the Runaway Technologies line, but it has been designed with Knight’s Armament for military applications and includes ballistic tables for specific issue rifle and ammunitions setups, such as the KAC M110 with M118LR ammunition. BulletFlight M also features an internal accelerometer that calculates the angle to the target if the phone is mounted perpendicular to the rifle’s bore.

 

 

 

 

Editor's Note: This article originally appeared in the July 2018 issue of Gun Digest the Magazine.

AR Basics: Under Gassed? Check Your Gas Rings

Before you crack into the gas system proper, it's good practice to check the status of your gas rings.

Worn gas rings effects and how to identify them:

  • Bolt will fail to lock.
  • Brass ejects to the rear.
  • To test gas rings remove the BCG and extend the bolt.
  • Stand on the bolt face, if it supports the weight they're good.
Editor's Note: This is the fourth article of four-part series dealing with direct impingement operated ARs and troubleshooting the gas system. Please check out Part 1, Part 2 and Part 3 of the series.

If your AR is still exhibiting cyclic performance issues after a good cleaning and lubrication, followed by the replacement of the buffer spring and maybe the buffer, you may have an actual gas system problem. With a clean weapon and a properly matched buffer spring, your bolt should be consistently locking to the rear on the one-round test and throwing casings within a few degrees of 3 o’clock on the angle test. Remember, a bolt that locks to the rear and throws brass toward the middle of the range is generally good to go and will continue to perform reliably if kept clean.

Retro-AR-Feat

There are a few other items to consider, and while they’re not rocket science, they are more complex. An under-gassed gun (one that fails to lock the bolt to the rear in the single round test and/or throws brass south of 3 o’clock on the angle test) may have worn gas rings.

The traditional field test for the gas rings is to remove the bolt carriage group, pull the bolt head full forward, and stand the assembly upright on the bolt head. If the bolt head supports the bolt carrier without it sliding down, your gas rings are likely serviceable. If not, replace them. Worn or ill-fitting gas rings allow excess gas to past through the internal piston and not backward into the buffer spring system where it belongs.

If you find yourself in this boat, Bravo Company Manufacturing sells a SOPMOD bolt upgrade kit that will not only get you new gas rings, but also a new USGI extractor, ejector and appropriate springs for about $30. It’s one of those repairs you might as well make all at once, and a fresh extractor and ejector never hurt anyone.

Step 1 Remove the bolt carriage group, pull the bolt head forward, and stand the assembly upright on the bolt head. Step 2 If the bolt head supports the bolt carrier without it sliding down (left), your gas rings are good. If not (right), replace them. 54
Step 1 Remove the bolt carriage group, pull the bolt head forward, and stand the assembly upright on the bolt head. Step 2 If the bolt head supports the bolt carrier without it sliding down (left), your gas rings are good. If not (right), replace them.

If you’ve invested what is likely less than $50 for all these new parts (about the cost of a single hour from your gunsmith), actually cleaned your AR, and it still won’t lock to the rear after the single round test or has extreme or inconsistent angles of ejection, you may have a real gas system problem.

It could have several causes, such as the gas block coming loose from the barrel, a Franken-gun mismatch of parts or amateur gunsmithing. Take it to a qualified gunsmith, tell him what’s happening, and he’ll figure out the rest. He’ll likely have to replace or re-fit the gas block. Yes, it could be the bolt catch/release, or several other small items, but you have covered 90 percent of the basics and learned something in the process — probably that your gun was just really dirty.

AR Basics: Issues That Mimic AR Gas System Problems

Informal tests might suggest an AR's gas system is to blame for a carbine's issues, but there are false positives that can muck up troubleshooting efforts.

What AR issues mimic gas system problems:

  • Dirty extractor, bolt face, ejector and bolt carriage group can fail to function.
  • Underluberication accelerates how quickly components get dirty and malfunction.
  • Mismatched buffer and buffer spring can make a rifle seem over or under gassed.
  • Buffer spring weakens and does not eject cases with the force it did when new.
  • Buffer weight can affect how a rifle cycles.
Editor's Note: This is the third article of four-part series dealing with direct impingement operated ARs and troubleshooting the gas system. Please check out Part 1 and Part 2 of the series.

A direct impingement system is a just that — a system — with multiple factors that can influence performance. Stoppages that might be attributable to a gas issue can be caused by something else, so let’s consider some other major variables that might skew the two previous test results and give you a false positive on the failure of your gas system.

AR-15-Sling-Lead

Adequate Bathing Required

When was the last time you cleaned and lubricated your AR? Yes, I know this sounds like the IT guy at work telling you to turn your computer off and back on to fix a software problem. But in this case, examining the cleanliness and lubrication of the action is critical.

The downside of the direct impingement gas system is that it dumps hot, dirty exhaust gas through the action — the specific area that needs to stay the cleanest and most lubricated. Many have likened this design element to “flushing the toilet through the living room” or other such unsavory analogies. The problem is, it’s true.

The hot gases, carbon and unspent powder running through the action are an unavoidable byproduct of the design. Worse, the hot gases bake the carbon onto the metal, ultimately changing the geometry of the parts and impacting how they interact. Add to this any dust and debris the action picks up from wherever you’re firing, and you truly have a “hot mess” on your hands.

ar-bolt-carrier

The most problematic areas are the spaces between the extractor and the bolt face. If this spring-loaded part cannot get over the rim of the cartridge to gain purchase, the AR will frequently or completely fail to extract the spent casing. The same is true of the ejector. In short, if these parts cannot work nearly simultaneously and in concert with the cycle of the bolt carriage group, the casing will eject poorly, inconsistently or not at all. These two areas must be examined regularly for contamination and carbon build-up.

Excess contamination also creates additional friction that impedes the bolt carriage group from cycling at the proper speed and force, which can prevent the bolt from fully reaching its rear-most point of travel and locking to the rear. It may also just slow the bolt enough to make it look like the ejection is weak. So, before you grab a wrench and go diving into your gas system, thoroughly clean your rifle, and make it a habit to use a high-quality lubricant and keep these parts clear of debris.

Buffer Spring Replacement

The second most common culprit behind a false positive on a gas system failure is a weakened or mismatched buffer and buffer spring. These two parts, depending upon their configuration and condition, can exhibit symptoms of an over- or under-gassed system.

If you have a reliable AR that, over time, starts throwing rounds nearer to the 1 o’clock position in the angle of ejection test, it may just be time to replace the buffer spring. Buffer springs are made to reliably cycle thousands of rounds, but like any metallic part put under stress, they weaken over time. If your rifle has functioned reliably for a reasonable amount of time before showing gas-related symptoms, it’s probably a combination of the spring weakening and the gas port diameter widening slightly over thousands of rounds. The result is higher pressure on a weaker spring, resulting in greater force to the rear and a more violently ejected casing.

Buffer springs can and do break down over time. The size of a carbine-length buffer spring is about 10 1/2 inches and needs replacing if it measures less than 10 inches. A rifle length buffer spring measures 12 3/4 inches and definitely needs replacing as it nears the 12-inch mark.
Buffer springs can and do break down over time. The size of a carbine-length buffer spring is about 10 1/2 inches and needs replacing if it measures less than 10 inches. A rifle length buffer spring measures 12 3/4 inches and definitely needs replacing as it nears the 12-inch mark.

A buffer spring is a cheap fix, usually $10 or less. Though exact specs can vary, particularly among custom race guns, a carbine-length buffer spring will be around 10½ inches new, and shouldn’t be any shorter than 10 inches after extended use. If yours is, and the gun is running hot — meaning it’s over-gassed — spend the change out of your ashtray and buy the new spring.

Note: Be sure to buy the correct buffer spring for your AR. A carbine length spring will have about 37 coils, give or take — count them as well as measuring the entire spring. In contrast, a rifle-length buffer spring will be about 12¾ inches new and is a candidate for replacement when it shortens through use to less than 12 inches. Also, a rifle-length buffer spring will have about 43 coils.

The carbine and rifle buffer spring lengths are not interchangeable, and it’s inadvisable to try. A buffer spring is a cheap fix, or at least the elimination of a variable, so buy one, test it in your clean AR, and you may likely solve your problem.

Buy A New Buffer

For about twice the cost but still less than $20, you can replace your buffer. Keep in mind, a heavier or lighter buffer can be used to tune the felt recoil of your AR system, and some shooters get picky about this part.

AR_buffers_02

In its simplest form, the buffer is a counterweight to the force of the gas imparted to the bolt carriage group, and it’s a device to compress the spring uniformly and alternatively press the bolt forward. For the average shooter, it’s not a particularly worthwhile place to get fancy unless you’re tuning for subsonic rounds or building a race gun.

A standard buffer, a little lighter or heavier depending on how your new spring performs the angle of ejection test, is OK — but over-doing experimentation with this part of the troubleshooting can be low-yield, if not downright irrelevant for a general-purpose AR.

Editor's Note: The article originally appeared in the May 2018 issue of Gun Digest the Magazine.

AR Basics: Initial Diagnosis Of AR Gas System Issues

To troubleshoot an AR gas system, the first step is figuring out if the gas system is to blame.

How to tell your system is straight:

    • Shooters tend to blame the gas system for issues such as a failure to extract.
    • It is wise to eliminate other possible causes before turning to the gas system.
    • Most stoppages are due to magazine problems, a good place to start.
    • Firing a single round from a magazine is a good diagnostic.
    • If the bolt locks, you're likely not under-gassed.
    • To determine the power of your gas system you can observe the direction of ejection.
    • Brass that ejects forward gets more gas than brass that ejects rearward.
Editor's Note: This is the second article of four-part series dealing with direct impingement operated ARs and troubleshooting the gas system. To read the first article on the DI system, please go here.

The most complicated aspect of diagnosing a gas system issue is determining if the gas system is to blame. Typically, a shooter will experience a stoppage, such as a failure to extract or feed, and begin to wonder if it’s the gas system. Here’s a free piece of advice: Exercise a moment of patience and some basic deduction before blaming the gas system.

The first step in diagnosing an AR problem is to eliminate the most likely culprit: the magazine. Perform the "single-round magazine" test and, if everything checks out, the diagnosing from there.
The first step in diagnosing an AR problem is to eliminate the most likely culprit: the magazine. Perform the “single-round magazine” test and, if everything checks out, the diagnosing from there.

By this I mean first eliminate as many other possible causes as you can. There are a few tests that can be used to determine if your AR is over- or under-gassed, but the tests should be conducted before and after removing all the non–gas system possibilities. Luckily, these tests are quick and simple to conduct.

1. The Single-Round Magazine Test
This test involves nothing more than loading one round into a new or serviceable magazine. Most AR stoppages are due to magazine problems, so start with one that works. Load the magazine into the rifle and fire the round. What does this tell you? The key piece of evidence is whether the bolt locks to the rear after the round fires.

If the bolt locks to the rear, you’re likely not under-gassed. In other words, the direct impingement system has adequate pressure to press the bolt carriage group far enough to the rear to engage the bolt stop/release on an empty magazine. If the bolt does not lock to the rear, it might be your gas system. It also might be a broken bolt stop/release or weak ammo. The next test will help narrow it down.

2. The Angle Of Ejection Test
This test allows you to determine the amount of power your gas system is exerting into the direct impingement system by observing the direction the spent brass flies upon firing. This test is best accomplished on a bench beside a table or with extra bench space to the right of the rifle (on the ejection port side).

Imagine the deflector (the triangular profusion of metal just behind the dust cover or opening for the bolt group) is the center of a clock. Mark this position and make sure the AR is placed here for every shot. Perpendicular to the line of the bore (direction of the barrel), directly to the right of the deflector, imagine that’s 3 o’clock.

Each time you fire a round, the AR should be oriented directly down range, and the deflector is in the same place. You can even use a marking device such as blue painter’s tape to mark the 3 o’clock position, as well as the 1 o’clock and 5 o’clock positions for reference. The brass will be moving quickly, so the marking tape will make the visual tracking easier.

The "angle of ejection" test is a simple way to determine if your gun is over- or under-gassed, or if it's right where it should be.
The “angle of ejection” test is a simple way to determine if your gun is over- or under-gassed, or if it's right where it should be.

With the AR pointed directly down range and the deflector in the center, fire a single round and watch the path of the brass’ flight. It might help to have a buddy stand to your left and do the spotting. Where does the brass fly? In general, this test measures the strength with which the spent casing hits the deflector — said another way, how much force the gas system is putting into the action.

Presuming all other elements in the system are otherwise functioning properly, brass that flies through the upper half of the arc, between 3 and 1 o’clock, is getting more gas than brass that flies through the lower half of the arc (between 3 and 5 o’clock). Keep in mind, this is a relative measure of the combination of your specific rifle, its level of cleanliness, its age and your choice of ammo.

Editor's Note: The article originally appeared in the May 2018 issue of Gun Digest the Magazine.

AR Basics: Understanding Direct Impingement ARs

Most AR rifles utilize a direct impingement gas-operated system to cycle. Understanding this system is key to troubleshooting it.

How a DI goes about its business:

  • A majority of ARs operate off the direct impingement cartridge gases.
  • The system consists of a port, block, tubes and a gas key.
  • A small amount of gas is siphoned after a round is fired and is diverted to cycle the rifle.
  • Generally reliable, the system can have a number of issues that can make it malfunction.
Editor's Note: This is the first article of four-part series dealing with direct impingement operated ARs and troubleshooting the gas system.

Not to be confused with gasoline, the gas-operated AR functions by using a portion of the propellant gases created by the discharge of the cartridge. The gases are directed back through a system of ports, blocks, tubes and a rotating bolt, and it ultimately compresses a spring to cycle the AR’s action. This efficient system functions to reload the weapon each time it’s fired and also to reduce recoil. It does have some drawbacks, which we’ll dive into later.

DI-Lead

Functionally, the direct impingement system is a circular sequence that runs as long as the operator continues to pull the trigger and exhausts the ammunition. After the first round is fired, the process starts on the barrel where a small hole, or gas port, vents a portion of the gas discharged after the projectile passes. The gas is vented into a gas block that regulates the amount of gas fed back into the action through tubes that run parallel to the line of the rifle’s bore. The gas block may be fixed or adjustable, and in some ARs it can be tuned like the carburetor on a car.

Lean or rich, the gas then passes through a gas tube into the gas key staked to the top of the bolt carriage group. This gas key absorbs the punch of the gas’s discharge, pressing the bolt carriage group back into the buffer and buffer spring, which are located in the rifle’s butt stock. The buffer spring compresses to the rear while, simultaneously, the bolt extracts and ejects the fired cartridge casing.

When the compressed spring recoils, the bolt carriage group travels forward, picks up another round from the magazine, and then reloads and re-cocks the weapon as it returns to battery. The rifle is now ready to fire another round when the trigger is depressed.

So what does the average shooter need to learn from all this engineering? First, the AR’s successful function depends upon re-direction of the appropriate amount of this discharge gas. Second, this system, though generally reliable, has failure points that can be tough to spot. And finally, the “magic gas” this system depends upon is hot, dirty and filled with carbon and unburnt powder that, over time, will impact the function of the parts and the system as a whole.

Editor's Note: The article originally appeared in the May 2018 issue of Gun Digest the Magazine.

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