M4 upper CMMG vs. RRA


October 12, 2004, 10:38 AM
I want a RRA M4 upper, but nobody seems to have the chrome lined barrels in stock, so I was considering paying a bit more for the CMMG upper. How much better, if any better is the CMMG upper, I know that it has feed ramp cuts, and T markings, but I have no idea how the T markings benefit me, or what they are even for. Can someone shed some light on my situation? My complete lower receiver will be shipping out tommorrow, and I want to make a decision soon.

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October 12, 2004, 12:28 PM
All complete upper receivers have feed ramp cuts, it is just a question of which style they are. Normal feed ramp cuts stop at the end of the barrel extension and don't continue into the stripped upper itself. M4 style ramps are longer, and require deeper cuts in the barrel extension that are continued into the upper itself.

The "T" markings are nothing more than position indicators on the rail... if you are swapping optics or whatnot from one upper to another, and know that you want them at an exact spot on the rail, you can always place them at, say, "T8" for example, no matter which gun you are using.

October 12, 2004, 12:32 PM
I just got one of these CMMG uppers last week. It's a really nice upper - mil-spec, 4150 steel, chrome lined, dremeled M4 feed ramps, 1/7 twist barrel, t numbered upper - all the cool features.

The 1/7 twist of the CMMG is a big plus over the 1/9 of the RRA uppers IF you are wanting to shoot the heavier (75+ grain) rounds. If you won't be using these heavy rounds then it is a wash.

The feed ramp cuts are either great, or worthless depending on who you believe. My own experience with non-feed ramped uppers is that some softpoint rounds may not feed correctly at times, so I think the ramps are nice to have.

The T markings are used to designate the different points on the rail. That way if you are using a nice, repeat zero mount for your optic you can be sure you are mounting it back to the same rail position every time. The markings also match the markings on KAC RAS units.

October 12, 2004, 12:38 PM
Did you check ADCOfirearms.com for in stock status on the RRA uppers?

I thought I saw some there when I was in 2 weeks ago.


October 12, 2004, 12:43 PM
dremeled M4 feed ramps

Are they dremelled after assembly, or do they use a real deal factory cut barrel extension and upper?

October 12, 2004, 12:47 PM
Yeah, I called Adco this weekend, he is out of the chrome lined M4 barrels, and he says he doesn't know when to expect more in, so if he has more in by the time I'm ready to order, I'll go with that, otherwise I'm leaning towards the CMMG. I know I will mostly shoot the Win. white box 55 grain ammo, but I'll also have some heavier hollowpoints on hand for home defense, so the 1:7 twist will be nice for that. This will be my first AR type rifle, and I want to do it right the first time, and save some money while I'm at it. Thanks for the input guys, it's been very helpful.

October 12, 2004, 02:26 PM
I bought a stripped RRA A4 upper and put a busmaster barrel assembly on it. It worked great for me.
RRA has a real nice dark finish btw.

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