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TreyE15 01-23-2013 09:18 PM

Mil Spec/ Comm Spec
Trying to learn something new today. Anyone that can offer pros and cons (doesn't matter if its based on opinion or fact, but I do always prefer experience) on AR-15s in either spec. This includes parts and upgrades. I have a DPMS AR15 in Comm spec, and I know that has to do with sizing. Help?

Quentin 01-23-2013 11:43 PM

Well first, milspec vs. commercial tends to become important when you're talking about a duty/patrol AR. Something very similar to the military M4 (or sometimes M16) but usually a semiauto version. When talking about a target or varmint AR there can be advantages to deviations from milspec. Some deviations from milspec are considered good even with a patrol rifle, things like midlength gas on a 16" barrel and a cold hammer forged barrel. But barrel twist rate (1:7"), chrome lining, barrel steel, high pressure testing and MPI testing should be milspec. Same goes for the BCG - proper materials, chrome lining, HP/MPI, shot peening and proper staking. Those are the most important things I can think of.

As far as sizing, the commercial diameter receiver extension is larger than the milspec version. This is outside diameter so milpsec stocks won't fit on a commercial tube. Commercial (A2) sights are 0.04" shorter than milspec version so you can run in to zeroing problems if you put a third party rear sight (which are almost always milspec height) on your DPMS.

There's a lot more to it than that but it's a start anyway.

Sniper03 01-23-2013 11:43 PM


There are good commercial rifles and then there are others that the tolerances are not quite as good. Mil-Spec is a Military Specified Standard of + and - tolerance and dimensions on parts. Plus other things like specified material the weapon is made out of, rockwell hardness on certain parts, magnaflux operations required inspection to detect any cracks, weaknesses, of voids on the specific part. Issues regarding plating, finish and other things. I reality a lot of it is no actually necessary for the common person or common use. In fact on a lot of parts used by the good AR manufacturing companies who manufacture rifles have closer tolerances than those required by Mil-Spec. I have a manual on Mil-Spec of which a lot isn't even a consideration on my part. One that always comes up is which stock is best of the 6 Position Tactical Stocks the Mil-Spec or the Commercial. A Mil-Spec 6 Position Collapsible Stock vs a Commercial 6 Position Collapsible Stock. If it is a good quality commercial 6 Position Collapsible Stock for example like the one Rock River, Stag and others use are made of high grade materials. Their is absolutely no difference in quality or durability other than the Commercial Extension Tubes (Buffer Tubes) are slightly larger in diameter than the Extension Tube on the Mil-Spec 6 Position Collapsible Stock. The threads by the way are the same on both. The Commercial Extension Tube has a 5 degree angle on the rear of the Extension Tube while the Mil-Spec Extension Tube is straight up and down at 90 degrees on the rear. They Tubes and stocks are not interchangeable! Bottom line either part or any quality rifle will do just fine! Personal preference to be frank and of course some use the Mil-Spec designation as a sales hype tool. Although it does have it's merits because if it is true Mil-Spec it confirms it is of good quality. At least within the tolerance standard. Hope this makes sense! :)


TreyE15 01-24-2013 01:45 AM

That's a lot to think of. It does make sense though. I ran into the spec difference when I changed out my factory stock with a Magpul CTR. It was one of those moments that I showed my lack of knowledge.

If I understand both of you correctly, mil spec typically is more durable and offers small differences in measurements and materials, while by themselves offer no meaningful differences to a casual shooter. However, when having a true spec rifle as a duty, patrol, combat rifle this differences together add certain attributes for longevity, handles more stress, etc etc? Makes sense. Would a mil spec rifle have slightly different alloys or materials involved in its construction?

Quentin 01-24-2013 06:23 AM

Normally the receivers for both are the same, milspec 7075-T6 alloy and annonized to milspec. However there often is a huge difference in the barrel and bolt steel and other things mentioned above. There's no getting around it, for a serious duty rifle most commercial ARs fall short. Will you see the difference? It depends on usage, after all some police ARs only see a few hundred rounds a year.

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