Friday, August 31, 2012

The infamous Mil-Spec

M4 style AR15 rifle
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.
Buffer tubes
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 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.


  1. Very brief article but straight to the point, although I am afraid it will end in the depths of the web as anything intellectually or sensible ;-)

  2. I have always felt that the term "mil-spec" means lowest bidder. We all know that the government works on the bid system. The lower the bid=lower cost=not a necessarily well built item. But this topic is going to create a veritable fecal event on forum boards by those who "know" better. Good article.

  3. Post this up on and wait for the hate to come rolling in. I agree with you, but unfortunately a lot of the internet commandos there don't.

  4. Well said, MAC. Companies like LWRC, which exceed milspec get blasted because some if their parts are not of the standard, but yet the people doing the blasting don't understand that the changes are for the better

  5. Rawl bolts
    i like it AR15 rifle. thanks for sharing informations regarding ar15

  6. Having worked in Mil. Acquisition, yes, many standards are woefully out of date, but sustainability and cross compatibility is really the main purpose and establishing MINIMUM standards of acceptable quality, form, fit and function. "Lowest Bidder" is somewhat of a fallacy for there are numerous different contract specifications that look for best value, sole source, etc. So Tim Smith certainly doesn't see the "real" picture, or at least not a complete one.

  7. Mil Spec will not develop a better gun. Having worked with Mil Specs during my twenty-three year career taught me that they have a terrible track record of keeping up with developments in materials and other design functions. In fact, most Mil Specs are never changed; they issue a new one and often forget to take the old one out of the loop. While Kurt worked in acquisition I worked on the results of that acquisition and had to submit a lot of change requests. Mil Spec changes often take years depending on the workload, workforce, and prejudices of the people reviewing them.
    Materialistically I have worked with Mil Spec materials from destroyers to aircraft and aircraft carriers. I have used the M-16, M-16A, and M-16A1 and I can tell you that there was plenty of room for improvements. Lets look at the M-16 that the USAF bought, the Mil Spec didn't require cleaning gear for the troop in the field as it was supposed to be Self Cleaning. Ask anyone who used those first M-16s about no cleaning gear and no forward assist (also not in the Mil Spec). I've worked on iron bombs, guided missiles, rockets, machine guns (from the A-7E/F-14 Gattlin Gun to the BAR, Thompson, and Grease Gun) and nuclear bombs. All of those munitions had Mil Specs. The ones with the longest life tend to have Mil Specs written by joint service groups while the worst are written by one service; witness the M-16 which didn't work in the jungle or Alaska or, after a couple hundred rounds, anywhere.
    Mil Specs allow for the military to ensure compatibility, within an operating range. Obviously the original Mil Spec for the M-16 sucked! Even after they "fixed" the problem by issuing cleaning gear and guns with forward assists (two changes to the Mil Spec), most of the Marines I knew would have preferred to keep their M-14s. Its interesting how that platform remains a preferred rifle for longer range shooting.
    Well, there you have it, Mil Spec by someone who had to deal with it for twenty-three years. Sure, the concept is excellent, but the delivery is often less than good.
    One last note: If you want a Mil Spec M-16-type rifle, you will need to get one that requires a Stamp for a Class III Weapon as the Mil Spec for the M-16 and its family requires selectable fire. Without selectable fire you haven't got a Mil Spec Rifle.

  8. Complete agree with the misuse, abuse, lack of understanding and even the fervent, fanatical and almost religious mantra that MILSPEC has become. In many cases you could replace MILSPEC with "Global Warming" and not miss a beat.

    BTW, I think you meant to say DLA is responsible for developing MILSPECs, not GAO. DLA is tasked with providing parts for many systems in the military and they use the MILSPEC to help them describe what it is they wish to purchase. The whole MILSPEC process is interesting in that DLA has conferences with various contractors to help them describe what it is they wish to purchase. In the instance of the AR, the MILSPEC was developed for each individual part before it was ever described as a system. This was because Colt owned the proprietary design of the M-16/M-4, even though DLA was tasked with buying replacement parts. Therefore DLA could not pull the TDA (tech data package) for a description of individual parts but had to develop each part's MILSPEC one at a time. Fairly recently PEO Soldier purchased the desgn and TDA for the M-16/M-4 and now the US government owns the system spec for the M-16/M-4, even though they have long ago developed all of the individual MILSPECs for each part.

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