Every group has a vocal cadre that demand compliance to their closely held beliefs as defined by their collective. In the AR-15 realm we have the mil-spec advocates. These folks have their short list of approved manufacturers and the moment a new company dares to come into existence they pounce to question every minute detail about the materials and processes used to manufacture the interlopers new wares.
Often times the criticisms leveled against the manufacturers’ products will be centered on compliance to military specifications. Ironically, most who cite the military specifications for rifles such as the AR15/M16 have never read the actual specifications nor even know where to find them. They instead resort to parroting what they’ve read on Internet discussion forums.
What are military specifications (mil-spec)? Simple, they’re standards established by the General Accountability Office (GAO) for defining essential technical requirements of purchased materiel for the military or for substantially modified commercial items to be used by the military. These standards have been established to guarantee interoperability, commonality, reliability and cost of ownership to ease the strain on logistics systems.
What mil-specs aren’t are a guarantee the product defined is the absolute best that it can be in terms of materials used or processes used for manufacturing. In the case of the AR15/M16 many of the specifications were established in the 1960’s and 1970’s long before various alloys were developed or even before CNC machining was in common use.
Take the buffer tube (receiver extension) of the AR15 rifle as an example. The military standard tube will have a diameter of 1.148”. The commercial buffer tube will have a diameter of 1.168”. The threads will be slightly smaller in diameter on the commercial tube (1.170’ vs 1.185”) as well. Some commercial tubes will have welded end caps where mil-spec tubes will consist of one piece.
Is the thinner mil-spec tube stronger than the thicker commercial tube? I guess that depends on what tests are conducted. In a real world application would a commercial tube be any more likely to fail if exposed to the same stresses as a mil-spec tube? Everything I can find would indicate no, the mil-spec tube isn’t necessarily more durable or able to withstand significantly more stress than the commercial variant.
So why do we have mil-spec on buffer tubes? Simple. If we go back to the definition of what mil-spec is we’ll find in this case it has to do with interoperability and compatibility. A Soldier should be able to remove a buttstock from one M4A1 and drop it onto another M4A1 without having to worry about compatibility. That’s it.
Another example would be the use of Carpenters 158 steel in the construction of AR15/M16 bolts. Carpenters 158 is the mil-spec standard material for manufacturing a bolt, but is it the best material available? Lewis Tool & Machine (LMT) thinks that Aermet is vastly superior (2.5 times stronger) to Carpenters 158. Their Enhanced Bolt, which is designed to remedy failures associated with the mil-spec standard M16 bolt, seems to be a popular item. This goes back to the specifications written for the M16 being drafted in the 1960’s and 1970’s. Better materials now exist yet the mil-spec standards haven’t been modified.
All the mil-spec advocates will claim the use of Carpenters 158 is a must. They’ll cite the infamous “Chart” hosted by M4Carbine.net as their holy scripture on the subject, yet in reality Carpenters 158 is a minimum standard and nothing more.
If you’re new to AR15’s and don’t know what to look for when buying a rifle from one of the 50+ makers of AR’s out there today, stick with mil-spec standards to get started. Or, do your research and find out where deviating from the military specifications can be a good thing.
There are some specifications you don’t want to deviate too far from such as MP/HP testing of bolts and barrels that assure quality and durability. Staked nuts on the gas key are a good thing as well. Having .154” diameter pins for the fire control group is another good thing (Colt used larger holes at one time). M4 feed ramps on a carbine are a bonus as they improve feeding reliability.
I don’t completely discount military specifications for the AR15 or think they’re totally irrelevant to the civilian legal AR15. What I do believe is that they’re a bare minimum standard for quality and interchangeability and nothing more.