AR's: Mil-spec or commercial?????

[Mtbkski]

OK, I bought an AR off someone. Wanted to change up some parts and make it look the way I want. Buddy of mine said to make sure I get the right size parts. He asked me if the parts were either Commercial or Mil-Spec. Hell, I don't know.

Question is, how do I know what is on the AR I have? Sure hate to end up buying stuff I can't use.

[39flathead]

Mil-spec comes into play when you are talking stocks.

The general rule is that if your buffer tube is flat on the back it's Mil-spec, if it's slanted, it's Commercial.

Mil spec is a smaller diameter 1.148"
Comm is 1.168"

[TaePo]

Would the caliber marking also determine it?

Or are there commercial spec 5.56? The converse then would be if any mil spec are .223?

[Hagbard Celiene]

I've seen Mill-spec thrown around a lot, but as far as making sure new parts will fit, as stated, the stock is the only thing that will matter. The tube will be a different diameter. The way I see it, if you didn't uy an M16 or M4A1 then its just a designation as to processing of materials and shapes of certian parts, such as the buffer tube. Chambering is a whole different story, and can be .223, 5.56, Wylde .223, or some other varient. to trully be a mil-spec barrel, I would assume it would have to be a 5.56 chamber, but I'm sure someone will come alongand correct my mistakes.

[TaePo]

I've seen Mill-spec thrown around a lot, but as far as making sure new parts will fit, as stated, the stock is the only thing that will matter. The tube will be a different diameter. The way I see it, if you didn't uy an M16 or M4A1 then its just a designation as to processing of materials and shapes of certian parts, such as the buffer tube. Chambering is a whole different story, and can be .223, 5.56, Wylde .223, or some other varient. to trully be a mil-spec barrel, I would assume it would have to be a 5.56 chamber, but I'm sure someone will come alongand correct my mistakes.

Well, eventually some person would get the idea and build an oddball type anyway just to do it... And to be able to prove everyone wrong!

[39flathead]

Every company and their brother advertises their stuff as "Mil-Spec".

Unless you truly have some oddball, the entire rifle except for the stock and buffertube will most likely accept any parts sold as "Mil-Spec".
If your buffer tube is mil-spec as I described above, that's all you need to worry about.


Your bigger concern should be whether or not you need Carbine, Mid or Rifle length when you choose your handguards if you are swapping them out.

Any grip and other add-ons will most likely fit your rifle with no problems.


What brand did you buy?

[Mtbkski]

Your bigger concern should be whether or not you need Carbine, Mid or Rifle length when you choose your handguards if you are swapping them out.

Any grip and other add-ons will most likely fit your rifle with no problems.

I'm pretty sure it is Carbine length. But I am new to the AR thing. (I carried an M-60 in the Corps. So, I never had the AR drilled into my head. )

What brand did you buy?

It was a build that someone put together, so it isn't a "brand". Variety of stuff to build it up.

[Gun]

That is a 16'' carbine length barrel. The lower receiver is polymer. Acquiring parts and assembling them is just as much 'building a rifle as the rifle being mil-spec.

It could have a 223 chambering or a 556 chambering. This should be stamped on the barrel, along with the twist (Info on this can be googled).

Would the caliber marking also determine it?

Or are there commercial spec 5.56? The converse then would be if any mil spec are .223?

5.56 NATO round was originally chambered in the M-16. Have not heard or read of any M-(something) rifles chambered in a 223.

[Mtbkski]

It could have a 223 chambering or a 556 chambering. This should be stamped on the barrel, along with the twist (Info on this can be googled).

When I got it off the guy, he told me it would shoot both .223 and 5.56.

[bluetrane2028]

If the barrel is stamped 5.56 it will shoot either safely, but if it is stamped .223, then only feed it .223. 5.56 operates at a higher pressure, and it can cause major issues when used in a .223 only rifle.