Since the AR 15 was originally designed for military use, it stands to reason that mil-spec—or the military standard—parts are going to be some of the most well-designed options out there for customizing your AR. When we talk about mil-spec in the strictest sense of the word, we’re talking about the standards set forth for various firearms by the U.S. Department of Defense. When people across the AR community talk about mil-spec parts, it’s often with this sense that mil-spec is the only way to go. But isn’t the primary perk of any AR that it can be customized based on individual needs and preferences?
Let’s start this discussion off with a broad caveat: unless you’re getting your AR 15 direct from Colt or Fabrique Nationale d’Herstal (FNH), the two currently contracted manufacturers of the M4 and M16, your AR isn’t technically mil-spec. And since you’ll be hard pressed to make that happen without a lot of hoops to jump through and a great deal of expense, odds are good that any mil-spec AR 15 you see on the market isn’t truly mil-spec.
Now, with that caveat out of the way, we’ll offer a bit of a clarification. Since there is a technical manual that lays out the technical specifications for every single part of an M16, it is, in theory, possible to build an AR that meets those specifications. While that build won’t be mil-spec in the strictest sense of the word, it is possible to buy an AR that gets pretty darn close, or find the parts necessary to modify it according to the D.O.D.’s standards.
Finding Mil-Spec Parts
If you’re dead set on having a mil-spec AR 15, and you’re willing to overlook that slight technicality in terminology, have at it. We will caution you, however, to pay attention to the specs of each piece as well as the price. Often, manufacturers calling a part “mil-spec” is a bit like saying something is wedding-specific—it adds more to the price by dint of the heightened demand. So, if you’re really interested in a mil-spec firearm, you’ll want to start by getting a hold of the D.O.D.’s manual for the M16. It may sound tedious, but what designates mil-spec are all of those nuanced specifications about each dimension and tolerance. So, if you really want mil-spec parts, the best bet is to go piece by piece and find parts that match the designated dimensions and tolerances, rather than relying on components being marketed as mil-spec.
Does Mil-Spec Matter?
See, the thing about mil-spec is that these are parts designed to a specific set of needs. When the M16 was commissioned, the primary functions were for a lighter weight, select-fire rifle that could chamber .223 (5.56 mm) rounds and maintain a high velocity. Basically, the need was for a lighter firearm that could fire a smaller high-velocity round so servicemembers could carry their firearm and more ammunition more easily without losing anything in firing power. Of course, civilian owners don’t necessarily have the same needs. So, while you’ll still enjoy some of the same benefits, getting away from mil-spec and, say, adding a KMR handguard or a semi-auto carrier group instead of the full-auto may actually be more beneficial based on your intended use.
What To Look For
If you do want to stick to mil-spec, there is one other thing to note. When you’re looking around for mil-spec parts, the biggest difference you may find is that some components meet the dimensions and tolerances demanded of M16 parts, but they may come with a different coating or be billeted instead of forged. If the dimensions and tolerances match up to the mil-spec requirements but the finish is different, it won’t be considered a mil-spec part. However, a difference in finish may serve to make that piece more durable or help fire more smoothly. If you’re interested in mil-spec, pay attention to the dimensions and tolerances, but feel free to branch out in terms of finishes. This could make for a better build and potentially save you some money. Just be sure you take the time to read reviews and do a bit of research into the materials and coatings before you purchase, so you know what to expect.