Let’s Bash: The “Combat-Reliable” AR-15 Build

TFB ran an article about a so-called “Combat-Reliable” AR-15 build. It’s silly.

First, the concept is dumb. What does “Combat-Reliable” even mean? Looking at the parts list, lots haven’t been used in actual combat. And that would be “combat tested”. If you want a “combat reliable” rifle, here’s one, albeit one with a slightly longer barrel. And technically, without burst or auto fire capability. Let’s say you’re an army and looking to buy carbines. You’re not going to gucci it up and spec out specific parts. You’re going to call your preferred FMS-approved vendors, buy some M4s,1 and go have beers. You don’t want to bother with parts compatibility and testing. And carbines aren’t all that important anyway. They need to work. Savings can go into more important things like bombs and artillery.

And really, if we look at how many rounds are fired in combat, it tends to fall way short of the MRBS numbers on an existing Colt/FN/whoever M4. Not to mention that there’s a big supply chain for parts for boring old M4s already. If your bolt breaks, replace it. Which you can do with the existing supply system.

But ok. Let’s suppose we want to make a rifle as reliable as possible for our own reasons. Which is fine. That’s a thing we can do as a civilian with our own money. Let’s just not make too much of a fetish of combat. It’s not 2006 anymore. So let’s look at the particular parts.

Lower, why? Billet because it’s cool? There are other lowers (Radian AX556, LMT MARS) that do all this one can AND let you lock the bolt back from either side, so they do ambi better. The LMT is also forged, so it should be lighter. Billet lowers look awesome, but do nothing for reliability.

Upper: Why?! Again, are we picking this part because it looks cool? Fine, but don’t try to tell me it’s somehow “more reliable”. Why still have the forward assist? Where’s the reliability/functionality gain? If you want “more rigidity” (not that I think it matters), get the Vltor MUR. Otherwise, go forged. On the other hand, if this build was sponsored by San Tan Tactical, good on your for getting a sponsor, and why aren’t you touting their awesomeness for being part of your project?

Bolt carrier: It’s a standard full-auto spec carrier, which is a fine part. Let’s look at the coating though. There are a lot of coatings out there. Hard chrome is chosen here, but there’s also DLC/Ionbond, NiB and NP3 (nickel-teflon). What I have never, ever found is any actual data showing that these are actually better than the standard parkerization in field use. Yes, some coatings are harder or more naturally lubricative. But the AR-15 is normally run with oil on the carrier and bolt, and the mil-spec phosphate coating “holds” lubrication pretty well. Now, if you want to make the argument that some other, non-standard coating is better, you need to tell us what we’re trying to improve. NP3 is the slickest and DLC is the hardest, so those seem like obvious choices. Hard chrome is great for abrasion resistance, and it looks awesome, but these are internal parts and the existing phosphated carriers don’t really have a problem with abrasion.

Bolt: This is a standard bolt with a hard chrome coating. There are bolts out there made of better steel that have extractors with better tension and lugs that are more resistant to shear. If your goal is to make a super tough rifle, you should probably have one of those.

Rail: The centurion rails are a nice upgrade to a milspec rifle build because they fit the stock barrel nut and are freefloated. But this is built from scratch, so why use the “stock” barrel nut at all? Geissele Mk 16 (from the URGI) seems the obvious choice here, because MLOK is lighter, cheaper, and doesn’t require rail covers. Geissele claims that their rail is the most rigid, which is good if you plan on attaching lasers to it and are looking for the last 1% of awesomeness. Also, most aftermarket barrel nuts that are reasonably modern don’t require timing for the gas tube, which is great. As a builder, timing is an annoying step.

If you want to argue that quad rails are the right choice, you need to tell us why. Most people are going another direction, including USASOC. USASOC going mlok seems to indicate that it’s certainly tough enough. Even if you want to go quadrail, why 9″? Why not go longer and have more room for accessories/your hand/bracing on a support? I’ve seen no data indicating that quadrails are actually any better at retaining accessories, if that’s a concern. They’re also more expensive.

Gas block: Why bother with a folding front sight block in 2018? Irons are not your primary. Get a longer rail and put folding BUIS on that like a normal person. You can’t even make a durability argument here, because those still fold. A fixed FSB would be more rugged, but that’s not what you have here.

I would argue, like Ian and Karl did with the WWSD rifles, that buis are superfluous these days, but I recognize that not everyone agrees. If you want irons, get something that is made of better materials than the ARMS sights and is elevation adjustable. Those rear sights aren’t all that durable, and isn’t that our goal here? Not to use old parts from 2006?

Barrel: Why is midlength gas optimal on a 16″ We’ve just seen Crane testing show that midlength is better than carbine gas on a 14.5″ barrel. So maybe intermediate gas is better on a 16″. Also, that is a government profile barrel, and that is a stupid, muzzle-heavy profile. Either go with a lightweight profile to save weight, or go with a medium profile for better accuracy/automatic fire capability. The government profile makes no sense.

The chosen flash hider should be able to mount a suppressor. If we want “combat” suppressors, maybe the Surefire SOCOM ones that have seen combat. But in any case, suppressor capability should be there. Even the basic “A2” flash hider can mount some suppressors.

Stock: Again, a really old part. Why? There are better stocks. There are certainly tougher stocks, to the extent that such things matter.


  1. Or HK 416s, since those are about 95% M4. 

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