Want to build a .50 Beowulf AR or convert one you already own? You’ll need a .50 Beowulf upper. Here are some of the best on the market.
As discussed in our first .50 Beowulf article, one of the appeals of this cartridge is its compatibility with standard AR-15 lowers. When all it takes to convert an existing 5.56 NATO AR into a big-bore thumper is a .50 Beowulf upper, a new bolt and maybe a new magazine, it gives plenty of incentive to take the plunge.
Whether you’re looking to convert an AR you already own or build a whole new gun from scratch, we’ll go over what you need to know to pick the right parts to build or buy a .50 Beowulf upper.
What To Keep In Mind When Picking Or Building A .50 Beowulf Upper
The first thing to keep in mind when shopping for an upper—or piecing one together to assemble yourself—is what you're going to use the finished firearm for.
Is this a hunting gun? Is it for defense? Will it be a rifle, a carbine or a pistol?
If you have a serious purpose in mind, what you don't want to do is take chances on budget parts, a budget upper or on your skill as a builder–unless you're already well experienced. For most shooters who have serious work in mind for their big-bore AR, a quality .50 Beowulf upper that’s been preassembled by a reputable manufacturer will be the best bet.
You should also consider where you source your parts from. Because Alexander Arms is the inventor of the cartridge, it is considered the go-to for all .50 Beowulf guns, parts and ammo. This isn’t to say that other companies don’t make fine products as well, but it’s hard to shake the sense that the original manufacturer will have the most experience when it comes to making the best possible parts.
.50 Beowulf Upper: Build Or Buy?
When deliberating between building or buying any AR upper, it comes down to customization and cost savings versus quality assurance. It's just as true for .50 Beowulf uppers as it is for standard 5.56 NATO.
The choice is obviously yours, but if you intend to use your ‘Wulf in any setting where a malfunction would be more than a minor inconvenience, paying a bit more for a factory-assembled upper is probably the safer option.
Whether you’re a bear hunter trying to put meat on the table or a SWAT officer in need of a reliable breaching gun, it would be smart to buy premade and to buy quality.
Most prospective .50 Beo buyers don’t fall into one of those categories, however. So if you’re looking to build one for more casual reasons then piecing your own stripped upper together from parts can save you money and enable more creative freedom.
Pitfalls Of .50 Beowulf Uppers For The 5.56 Builder
Because the AR market is so dominated by 5.56x45mm components, there are a few important differences to keep in mind when dealing with .50 Beowulf parts compatibility.
.50 Beowulf BCGs And Bolts
The .50 Beowulf is something of a hybrid cartridge, as the case starts its life as .50 AE brass that's trimmed back and has its rim rebated to roughly the same diameter as 6.5mm Grendel.
The OEM bolt carrier group is a 6.5mm Grendel bolt with a .50 Beowulf bolt head. Since the rim is rebated to 6.5mm in diameter but a different thickness, you need a .50 Beowulf bolt. At a minimum, you might get away with a .50 Beowulf extractor on a 6.5mm Grendel bolt, but getting the purpose-built .50 Beowulf bolt itself is a good idea.
Some owners report cycling issues when using bolts and carrier groups not made by Alexander Arms (differentiated by being labeled 12.7x42mm rather than .50 Beowulf to avoid infringement), especially those based on 7.62mm AR BCGs.
Of these owners, a number have reported fixing the issue by replacing their bolt and/or BCG with an Alexander Arms-branded one. With a cartridge this unique and proprietary, it, unfortunately, seems buying OEM parts may be the best route to ensure reliability.
.50 Beowulf Handguards
When building a .50 Beowulf upper from scratch or modifying an existing one, handguards must be selected carefully. While many standard AR-15 handguards will work, many others will not as the interior diameter is too narrow to slide over the barrel and the gas tube. Before buying, make sure the model you’re considering has enough clearance for the thicker parts.
.50 Beowulf Magazines
Another common issue experienced with .50 Beowulf guns pertains to their magazines, but that is true of all semi-automatic firearms to a degree. Make sure you get quality magazines and vet them with your rifle and ammunition. If a manufacturer recommends a particular magazine, stick to it.
.50 Beowulf Barrels
More companies than you might expect manufacture barrels for .50 Beowulf (or 12.7x42mm), so there are options out there.
Most .50 Beowulf barrels have a 1:19 or a 1:20 twist rate, and 16 inches is the most common length. It should be noted that shorter and longer barrels exist as well. Stainless and chrome-moly steel are both available, as well as different barrel contours, optional fluting and even integral muzzle brakes.
The usual gas journal diameter is 0.875″ (there are some larger) and adjustable gas blocks are available from a number of manufacturers. Note, some barrel makers offer them as an upgrade with your order. It's worth thinking about the upgrade, especially if you're going to add a suppressor.
Fluting and other weight-reducing additions (or rather subtractions!) are available from some manufacturers, and this would be a good option to consider if you carry your carbine in the field.
When choosing a barrel material, keep in mind that even match-quality stainless steel barrels have a shorter service life before accuracy diminishes. The lower-cost 416R barrels wear even faster. A chrome-moly-vanadium (CMV barrel) with a nitride finish will retain accuracy the longest.
Other .50 Beowulf Parts
Aside from those components, the upper receiver itself remains the same, the dust cover is unchanged and all the lower receiver parts are the same spec as for 5.56 NATO builds. It is, however, recommended that you use a heavier buffer (H2 or H3) and a quality buffer spring (such as Springco Blue or Red springs) to improve reliability, as well as a good pad on the stock to help tame recoil.
The final consideration is the muzzle brake, which obviously must be large enough to accommodate the large-bore .50 Beowulf projectile and have a thread pitch compatible with your gun.
The 5 Best .50 Beowulf Uppers
Alexander Arms 16-Inch DIY Kit
Alexander Arms, the original creator of the cartridge, has several .50 Beowulf uppers for sale that can be mated with one of the company’s own lower receivers or any standard AR lower.
The 16-inch DIY kit includes a 16-inch barrel, a gas block, a gas tube, a BCG, a charging handle and a forward assist as well as a flat-top upper receiver, along with some other small parts. All you need to complete this kit is an assembled lower and a handguard of your choice.
A 12-inch DIY kit is available as well, in case you prefer a pistol version or perhaps an SBR with the appropriate tax stamp.
Upgrade options available include the ability to add a Radian ambidextrous charging handle, a muzzle brake and a free Alexander Arms hat.
MSRP: $850 // alexanderarms.com
Atheris A15-M 12.7x42mm Upper
Atheris has AR-platform rifles for sale in multiple calibers, including 12.7x42mm which is—of course—the generic equivalent of .50 Beowulf since Alexander Arms still holds the patent.
Atheris offers multiple barrel lengths, including 7.5-, 10.5-, 16- and 18-inch barrels. You can also choose to add a three-port muzzle brake (a good idea for this cartridge) as well as a Cerakote finish on the barrel, upper or both.
The Atheris upper includes a 416R stainless steel barrel, a nitrided Atheris BCG, a nitrided gas block, an ambidextrous charging handle, an Atheris M-LOK handguard and a flat-top receiver with a Strike Industries dust cover.
MSRP: Starts At $649.99 // atherisrifle.com
Pro 2A Tactical AR-15 12.7x42mm Uppers
Pro 2A Tactical offers three different uppers for 12.7x42mm, in 10.5-inch, 16-inch and 18-inch barrel lengths.
Flat-top upper receivers and M-LOK handguards by Bowden Tactical are standard, along with a CMV barrel with a heavy profile, 1:20 twist, low-profile gas block and a three-port muzzle brake.
The base uppers are flat black and come with no charging handle or bolt carrier group, but when ordering there are options for adding an FDE Cerakote finish as well as a mil-spec charging handle and BCG.
MSRP: Starts At $399.99 // pro2a-tactical.com
MMC Armory 12.7x42mm Build Kits
MMC Armory offers multiple build kits for 12.7x42mm, including 10.5-, 16- and 18-inch barrel kits, with different handguards and muzzle devices for each respective barrel length.
All MMC Armory build kits feature either an Aero Precision or Davidson Defense upper receiver, a CMV barrel, a low-profile gas block and M-LOK handguards. The exact barrel and make/model/length of handguard depend on which build package you choose.
You can order the kit unassembled for the base price, assembled for an additional $19 or assembled and test-fired for an additional $49.99. One can also add a Swampfox red dot for an additional $130. To complete one of these kits, all you’ll need is an assembled lower receiver, a bolt carrier group and a charging handle.
MSRP: Starts At ~$300 // mmcarmory.com
Alexander Arms .50 Beowulf AWS Upper
The top of the Alexander Arms range in terms of uppers is the AWS (Advanced Weapon System) upper, which features a 16-inch barrel, Midwest Industries M-LOK handguard and a Radian Arms Raptor charging handle.
You also have the option—as with all Alexander Arms .50 Beowulf rifles, pistols and uppers—to add your choice of muzzle device (Tank brake, Millennium compensator, or Pepper Pot brake) and whether or not you would like a complimentary Alexander Arms hat.
This is the most expensive .50 Beowulf upper on this list, but it is the OEM for the caliber. If you wanted a fighting or working carbine-length gun that's ready to go out of the box…this would be a top choice.
MSRP: $1,155.95 // alexanderarms.com
More Non-Standard Caliber AR Info:
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