Opinions on this upper from CMMG


December 26, 2006, 01:30 AM
18" SPR Barrel w/Mid Length Gas

New 18" Special Purpose Rifle upper. This upper is based on our M18 multi-role barrel and comes with mid-length handguards ,mid-length sight radius, and is complete with bolt, carrier and charging handle. CMMG semi auto bolt carriers have the shrouded firing pin to protect against hammer wear. Upper receivers are "T" marked and include extended feed ramp cuts. Features include medium contour barrel, 11 degree recessed target crown, mid-length gas system, chrome-lined 5.56mm chamber and bore, 1/8 twist, parkerizing under F marked forged front sight base and magnetic particle testing on every barrel. When ordering with optional gas block, barrels will not be drilled for taper pins. Barrel is marked CMMG MPC 5.56 NATO 1/8.

Over the last month or so I decided that I'm going to put together an AR-15. I've been thinking about this upper with either an ACE stock or an adjustable stock. I have been reading a lot of the threads about mid length and carbine length gas systems, especially the ones that Bartholomew Roberts has been posting with the explanations of what each type of system does. My other choice would be a mid length system with a 16" bbl. I like the longer sight radius and extra two inches of barrel but I am wondering if it is worth the extra weight. I want to keep the gun simple and keep the weight down. Any and all input is welcome. BTW, for the lower I'm thinking of a right handed Stag even though I am a lefty.

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Don't Tread On Me
December 26, 2006, 01:57 AM
18" midlength, 1/8 chrome lined...sounds like a winner. Is MP tested too. That's a big plus.

I'm not 100% sure that it's the true SPR profile, but even if not, it's close enough.

Usually SPR barrels are match-grade barrels. This seems like a service grade barrel, but that doesn't mean that it won't shoot well.

I was looking at that particular set up myself. I don't think you can go wrong with that.

Barrel profile is more important in being a weight factor than length is. The 18" length is a good compromise between the 16" and 20".

Bartholomew Roberts
December 26, 2006, 01:12 PM
At 18", you should be able to run a rifle length gas system with no problems and the pressures will be lower. I would probably go with a rifle length gas system on an 18" barrel and a midlength on a 16" barrel (17" is the shortest you can reliably run a rifle length gas system).

I have a CMMG barrel and am happy with it; but I have read a post on AR15.com recently that their external barrel dimensions were not consistent and it sounds like their may be something to that (although this was only one report). This will only be an issue if you mount a suppressor later.

December 26, 2006, 07:01 PM
Now I have to dive back into the internet and see who makes an 18 incher with a rifle length system. Maybe I'll just get a muzzle loader because the AR15 info overload is making me dizzy!;)

Bartholomew Roberts
December 26, 2006, 07:11 PM
The CMMG multi-role barrel comes in carbine, midlength and rifle length gas systems IRRC.

December 26, 2006, 07:23 PM
I just looked at their site and found the 18" with rifle length system.

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