CMMG upper issues

[SpaceWrangler]

Just curious... what are the brands of these various BCG's?

Are the Gas Keys tight and the screws properly staked? A loose Gas Key can allow enough gas to leak out that the Gas System won't function properly.

Also, are you running them all with plenty of lube? AR Bolts and Carriers vastly prefer to be run wet with good quality gun oil. The old Army / USMC rule of 'a light coating of oil' is simply wrong.

[JohnInNH]

I would return the Upper to CMMG for evaluation before I started drilling bigger holes or anything else that would void the warranty.

Warranty is already voided. here is what CMMG said:

...as for the warranty, since you have used re-loaded ammunition (Hornady 225gr Match, 10.5gr A1680, OAL:2.160", clocking 1020fps
average) , it has already been voided: http://www.cmmginc.com/pages/ammunition.html

I was thinking of getting an upper form them.. Not now so sure now.. I just started my net search on their CS and user feedback. Huge thumbs down reading this post.

NOTHING wrong with that load. A1680 and 225 gr and 1020 FPS = 100% safe. OAL in spec.

SO Just because it was a hand load they would not take it back to look to see even IF it was their fault? Geez even Remington 220 had 2 lots that had major FPS differences. Your ammo was right on for factory spec.

Now if returned and they said it appeared you Over Pressured the upper sure.. but that is just a freaking cop-out. Companies like that wrankle me..

You could have said it was factory ammo and sent it back.. But you KNOWING your load was not going to hurt the upper offered the data to them and they used it as an excuse to not even look into it. What if the upper had a problem and it WAS their fault and it could lead to an injury... ya think they might want to know if their assembly process has a problem.

They obviously do not give a crap about their quality.. Otherwise they woudl have offered to look at it and if was their fault covered it and if not made you pay both ways.

Again.. That attitude is BS.. Thanks for posting their IMPRESSIVE CS support you got.

"I can neither confirm nor deny if my upper had handloads in it." Send it back n let them determine the problem.. bad ammo than it's on you. But if the found an out of spec BCG (as an example) it's not the ammo!

This should be like with cars... just because you chipped you car does not mean you Power Steering pump is no longer covered.

[Quiet Riot]

I would return the Upper to CMMG for evaluation before I started drilling bigger holes or anything else that would void the warranty.

Warranty is already voided. here is what CMMG said:

...as for the warranty, since you have used re-loaded ammunition (Hornady 225gr Match, 10.5gr A1680, OAL:2.160", clocking 1020fps
average) , it has already been voided: http://www.cmmginc.com/pages/ammunition.html

They just screwed the pooch. I will be sure to mention this every time I answer a "which upper/barrel should I buy?" post.

[SpaceWrangler]

..

[JohnInNH]

CDNN Sports/TargetSportsInc has a 16" flat top upper for $400-$430 on page 31 With BCG and WASP lined bore (nitrated?)

I wonder if they would do the same thing .. Now at a place like that I woudl expect a slip shod excuse to void a repair.

I wonder if this is worth it .. the parts are about that much.

http://lib.store.yahoo.net/lib/cdnn/CDNN2011-4.pdf

[civilian75]

Just curious... what are the brands of these various BCG's?
Are the Gas Keys tight and the screws properly staked? A loose Gas Key can allow enough gas to leak out that the Gas System won't function properly.
Also, are you running them all with plenty of lube? AR Bolts and Carriers vastly prefer to be run wet with good quality gun oil. The old Army / USMC rule of 'a light coating of oil' is simply wrong.

* BCG brands are unknown. They have no obvious identifying marks.
* I took the gas block off the other day. I could not observe any obvious gas leak marks. But maybe I wasn't looking close enough.
* I run BCGs kind of dry per your standards. But will definitely take your input under advisement.

Now that at least I can get a full stroke, I am going to focus on my load. I am still getting a horrible velocity spread, which mortifies me. I am not a reload noob. I have developed very accurate subsonic loads for other platforms. Normally, I would change powders but in this case I know I am within specs. Using new primed Remington brass, opened a new jug of A1680 just for this project. Hornady bullets quality is typically better than acceptable. I am even insuring a get a good crimp with a Lee Factory crimp die. I running out of ideas, but won't buy factory ammo.

Next steps I got in mind:
* I have been so focused on fixing the stroking issue I have not been paying attention to properly breaking in the barrel. Next step will be to give it some needed TLC.
* Then, I will take that gas block out again and inspect it with more critical eyes.
* will reload the Rem brass but this time I will use CCI 400 instead of Remington 7.5 primers. (I wished I had some BR4 at hand).
* I have a handful (~10) of 240gr SMK I will also try.

[civilian75]

CDNN Sports/TargetSportsInc has a 16" flat top upper for $400-$430 on page 31 With BCG and WASP lined bore (nitrated?)

I wonder if they would do the same thing .. Now at a place like that I woudl expect a slip shod excuse to void a repair.

I wonder if this is worth it .. the parts are about that much.

http://lib.store.yahoo.net/lib/cdnn/CDNN2011-4.pdf

John, those prices aren't bad. Thanks!!

[SpaceWrangler]

Not the Gas Block on the barrel. The Gas Key is bolted on top of the BCG with two Allen-head screws. They can work loose sometimes.

[civilian75]

Not the Gas Block on the barrel. The Gas Key is bolted on top of the BCG with two Allen-head screws. They can work loose sometimes.

Oh, ok, I'll check. But keep in mind the upper failed with two BCGs. Both have one thing in common: new; not broken in.

[SpaceWrangler]

AR's built within the proper specs don't need to be broken in.

Coming from 1911's years ago, this is one of the things I really like about name-brand Mil-Spec AR's... nothing needs to be fitted, smithed, polished, or broken in. A Mil-Spec AR is truly modular, using interchangeable parts made to a very exacting specification. A Daniel Defense Fire Control Group will fit (and function) perfectly on a Colt, Noveske, Lewis Machine & Tool, FN, etc.

It's more of a crapshoot with hobby brands... gas ports can be too big or too small, chambers too tight, no staking, questionable metallurgy and heat-treating, etc. That's why I was curious as to where the various BCG's came from.