Gun Digest

Heavy Metal: Building An AR-10

If you want to compete in the Heavy Metal Division of 3-Gun, you’ll need an AR-10. Here are the basics.

When Heavy Metal Division began, iron sights ruled and life was good. Then a lot of shooters got older and found optics were better. Thus, Heavy Metal Tactical was born.

The High-Performance AR-10

The Heavy Metal division is a step back in time, especially when it comes to caliber and sights. A rifle used in Heavy Metal division can only be chambered in .308 Winchester/7.62 NATO.

You can only shoot Major ammunition, there is no Minor in Heavy Metal. So, that means a 320 power factor, and for a 150-grain bullet, that means a velocity of at least 2,100 fps. Since the factory loadings of .308 will usually fire a 150-grain bullet at 2,400 to 2,500 fps, making Major is easy. It is dealing with the recoil that is hard.

The Mega Machine .308, at the start.

A Heavy Metal rifle is allowed a muzzle brake, but it cannot be lager in diameter than 1 inch, nor longer than 3 inches. On a .223/5.56 rifle, a brake or comp that size is all you really need. On a .308 rifle, that is asking a lot of a brake. While a muzzle brake that small can take the sting or thump out of shooting a .308, it won’t make it as soft to shoot as that same size would on a .223.

You are limited to magazines that hold 20 rounds. In the beginning of Heavy Metal, only iron sights were allowed, but once more shooters wanted to try it (and the shooters who were doing it got a bit older),

Heavy Metal Tactical was created, and one optical sight was permitted. That is one sight, red-dot or magnifying, period. Heavy Metal Limited still does not allow an optical sight. No bipod, no flashlight, but a suppressor is permitted.

Heavy Metal was a way for traditional rifle shooters, or rather, shooters of traditional rifles, to compete, and not be put at a disadvantage compared to a tuned AR-15. Back in “the day” this meant M1As, FALs, the occasional Garand, and various HK rifles.

Now, with the advent of the modern AR-10 variant, you see AR-10s. When we started this, the only .308 ARs to be had were rarities, original AR-10s, usually select-fire. But now the .30 AR is pretty common, and that’s what you see.

I built mine on a Mega Machine receiver set. The receivers, barrel, bolt and handguard came as a set, and that’s all you really need to get started, because the rest of it is all standard AR-15.

Armalite makes a 7.62 rifle. The older version uses modified M14 magazines.

Yep, triggers, pistol grips, stock, those are all regular items out of Brownells or from AR makers that you can use to finish the build of your Heavy Metal thumper.

One drawback to the AR-10 is that there is no mil-spec, so, each maker has had to re-invent and de-bug the design themselves. Once you go with a maker, you are stuck with them for parts. At least, the proprietary parts.

As a result, you’ll find that you can do the externals and the common parts, and thank goodness, the magazines, in common.

Learn More About The AR-10:

Most will work with Magpul 7.62 magazines. One exemplar is Armalite. They started this before Magpul was around, and as a result, Armalite modified M14 magazines to work in their AR-10. So, there are older Armalites that use those proprietary magazines. Otherwise, everyone uses Magpuls.

So, you have to use the proprietary parts of the manufacturer. You get to use all the other standard AR-15 items, you get to use the most-excellent Magpuls, and you get to shoot a “real” rifle in .30.

What’s not to like?

Editor’s Note: This excerpt is from Gunsmithing the AR-15: Building the Performance AR, available now at

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