Not too long ago I purchased a CMMG/DPMS Pre-ban M4A3 upper. This upper has a 16", 4150, 1/7 barrel with a 5.56 chamber, fully chrome lined chamber/bore and M4 feed ramps.  

See the project details here ->www.ar15.com/forums/topic.html?b=3&f=12&t=162739

I just finished doing a reliability test on this upper using 5 types of ammo.  I fired 200 rounds each of the following ammo.

1.Federal XM193
2.Hot Shot SS109
3.Winchester Q3131a
4.South African M1A3
5.Wolf 55 gr

I let the barrel cool off in between ammo changes also there was no cleaning during the test.  I also fired Wolf last to see how it performs when it was already dirty.

Results - 1000 rounds fired with NO malfunctions and that nasty Wolf ammo just flew right through!

The chamber seems truly 5.56 and mil-spec!  The only thing different I have is the Wolff extra power extractor spring which I also run in my other carbine upper.

Afterwards without cleaning it, and using sand bags I shot 50 rounds of Black Hills remanufactured 77 gr. I was pleseantly surprised that shooting 1 MOA 5 shot groups was not difficult and if I did my part I was  even able to get several 3/4 MOA groups.  I have no doubt that this barrel can outshoot me and with someone more capable it could probably shoot sub-MOA all day long.

I'm very happy with this upper and barrel and would not hesitate to buy another one!

That being said I've also noticed a couple of posts about unreliable DPMS uppers and barrels and I was not too impressed with th answers given by the DPMS support people.  DPMS mentioned having tighter chambers yet still being 5.56 and a special list of ammo that will work reliably, etc, etc...  I don't know why the barrels made for CMMG seem so much better but IMHO the only DPMS barrels I would ever buy would be the ones specially made for CMMG.

Please note I have no business affiliation with CMMG, I'm just a happy and very satisfied customer!

Just a comment, but......sounds like it already has a capable somebody behind the wheel. [;)]

[blue]Nice post.[/blue] I believe I'll do the same thing.
I most likely won't use 5 different types of ammo just 2 or 3 and then the Wolf.
Nice standards for an ammo test!!

Well Good! This kinda sounds like you were suspecting it NOT to be 5.56. I hope that's not the case.

I'm planning to buy a whole CMMG DPMS M4 rifle in the next few weeks so every bit of info I can gather is useful. It will be a duty gun for me and I'm buying it instead of a Bushy, so it HAS to be reliable. Good POST!!

To be honest after reading DPMS's replies to several posts regarding chambers and ammo reliabilty I was not too sure.  

I just tested my upper the best way I knew how and let the chips fall where they may.[8D]

Please keep us posted on how your CMMG upper works!

What kind of groups were you getting with the 55gr ammo?I'm just wondering because I need a new upper and can't decide on 1/7 or 1/9.

I was easily able to 2-1 MOA with 55gr XM193.  Remember this is 5.56 mil-spec ammo so don't expect [b]MATCH[/b] accuracy with it.  

IMHO, between the 1/9 and 1/7 I would go with 1/7 because you will have more options regarding ammo selection.  The military has been using 1/7 for a long time and they have no problems with 55 grain ammo.

If you're getting a new bench rest upper then maybe a 1/9 or 1/8 would be better but for a fighting rifle I would go with a 1/7.  

As always, YMMV![;)]  

This would be for fightin'.I had thoughts that 55gr would be all over the place through a 1/7.Thanks for the review.

"The military has been using 1/7 for a long time and they have no problems with 55 grain ammo"

The military doesn't shoot 55grain ammo.

But I have put 50grain bullets through my RRA 1/8 DCM barrel and it puts em into about .4inch at 100yds so I would bet it would be OK.

Remember 1/7 was really utilized for the almost never used tracer ammo. Being smarter than the government (knowing wether or not you intend to use the tracer round and wether or not you need it to stabilize if and when you do) you can probably choose your own twist 1/8 is good for 50-77gr 1-9 is good for 45-62grain 1/7 might be faster than you need if you aren't shooting 80grain bullets.

The slower the twist rate the longer the barrel will last.

[b]The only time I ever fired tracer ammo through the M-16 was on a 50yd night qual course and at that range I bet stabilizing wasn't helping me hit the target (some light or night vision would have helped though).[/b]

Greeno,

I know the military doesn't issue 55gr/M193. You are correct, I should have been more clear.

I do remember my brother telling me that he used a ton of M193 for practice ammo and that guard units used a lot of M193 with their M16A2's.  Now this was back in the 90's so I may be a bit behind but I know a lot of 55gr was shot through military 1/7 barrels with no issues...[;)]

I really don't think there will be any issues using 55gr round with a 1/7 and it will allow you to step up to heavier bullets.  Tracers aren't the only reason to move up to a 1/7.  

Here's a few more good threads about the 1/7 twist.
[url]http://www.jobrelatedstuff.com/forums/topic.html?b=3&f=16&t=163070&w=searchPop[/url]

[url]http://www.jobrelatedstuff.com/forums/topic.html?b=3&f=12&t=163071&w=searchPop[/url]

I have been thinking of contacting ADCO to do a shortened conversion on a pre-ban CMMG/DPMS upper (for that "more correct M4A3 look"). They currently supply only the RRA uppers.

I know that this is a little off-topic, but is this a bad idea?

Sky9pilot,

I'm not sure about cutting down a 16" chrome lined barrel.  If you want a 14.5" upper then Bushmaster and CMMG both have 1/7 uppers/barrels.  I would probably just get the correct size barrel rather than cut one down.

yes, there are plenty of 14.5" barrels, so please don't reduce the supply of 16" by chopping one down. :)

Thanks Yojimbo and blikbok for the advice.

I have seen many accomplished 'smiths say that they will not cut down a chrome lined barrel, period, end of story. But ADCO's website...

I was wrestling with the 14.5" barrel question, but I understand that the A2 flash hider will not bring the overall length up to the required 16". I want the best of all worlds (cosmetic and function), but certainly don't want any FFA hassles.

On the functionality issue, and I'm sorry if I'm getting even further off-topic from this thread, I am worried that a shortened barrel will effect cycling and/or bullet drop should I migrate to a magnified optic.

ya know. If you think about it, I'm suprised we dont hear more about how reliable this new upper offering is.

It's a 5.56 chamber, chrome lined, AND has ramp cuts, which make it even less likely to fail-to-feed. Who else offers all that. COLT is the only one that I know of. Bushy's are great guns but even they don't have ramp cuts.

Anyway I'm just suprised by a recent post where someone said "help me buy a reliable AR" and no one even mentioned the CMMG/DPMS.

i built an M4 last year using one of CMMGs 14.5inch chrome lined DPMS barrels. if i understand correctly these barrels were made for a govt contract that they lost or had overruns or something. all i know is those DPMS chrome lined 14.5 barrels are the equal of any colt or bushie 14.5 ive ever seen. the price was good and CMMG are some of the best guys to deal with when it comes to honesty and service. i'd buy from them again. and i'd buy DPMS again as well

Actually these barrels, 14.5" and 16", are a CMMG custom order, to their (Mil-spec) spec's. While DPMS is the contractor, the barrels are only available from CMMG, and not from DPMS.

AFAIK, there are A2-lookalike FH of the appropriate length to make the 14.5 barrel non-NFA.  KKF may have one.

I have two of the CMMG/DPMS 14.5" uppers and both have proven to be very reliable and very accurate.  In fact, my post-ban (complete DPMS) is one of the sweetest shooting ARs that I've ever fired and my pre-ban upper (on a SGW lower) is damn close.  I think they are excellent barrels and uppers and wouldn't hesitate to order another one from CMMG.