10.5" vs 11.5" Barrels

[Iraqgunz]

That's odd. CMMG barrels usually have larger gas ports and are overgassed. In your case it sounds like it is too small. Did you ever bother to contact them and explain the issue?

I would consult with a knowledgeable AR person and ask them to measure the port and open it up. Once that is done I would think you would be fine assuming that all is assembled correctly.

I have a CMMG 10.3" SBR. The only way that I could get it to work reliably was to install the lightest buffer I could find (H1 I think) and use Federal M193. Prvi M193 does not cycle the action 100% of the time. Forget about commercial 223Rem. I have not tried heavier bullets. If I had to do it over, I'd definitely not go with a 10.3". 10.5" would be the minimum for sure. I'm now waiting on a stamp to be approved for a Colt 6933 (11.5" barrel). Can't wait to pick it up.

[Bret]

That's odd. CMMG barrels usually have larger gas ports and are overgassed. In your case it sounds like it is too small. Did you ever bother to contact them and explain the issue?

No, I started off by ordering a 9mm upper receiver. Instead of a real 9mm upper receiver (no forward assist) as pictured on their website, they sent me a regular A2 upper receiver. I returned it, but they would only give me credit towards another purchase. Since I had been wanting a 5.56x45 SBR, I ordered a 10.3" 5.56x45 upper half, receiver, and buttstock from them (all but the LPK). Unfortunately, they had an incorrect barrel profile picture on their website. They didn't send the one pictured, but rather one that was significantly heavier. The resulting rifle was very front heavy. It took a couple of months and many calls to get them to correct this. They actually had to reprofile the barrel. After going through all of this, I just did what I had to do to get it running. The whole thing was such an ordeal that I was pretty sour by the time I got the reprofiled barrel back from them. I just couldn't stand the thought of going through anything else with them. I think that they just had more business than they could handle at the time. Hopefully they've improved their customer service since then. I need to clarify about the PRVI M193. It throws the spent brass out 100%, but the carrier doesn't lock back after the last cartridge 100% of the time.


BTW, I ended up getting a factory Rock River 9mm SBR that is awesome, so I'm happy that things didn't work out with the CMMG 9mm AR15.

[usmcvet]

I have a CMMG 10.3" SBR. The only way that I could get it to work reliably was to install the lightest buffer I could find (H1 I think) and use Federal M193. Prvi M193 does not cycle the action 100% of the time. Forget about commercial 223Rem. I have not tried heavier bullets. If I had to do it over, I'd definitely not go with a 10.3". 10.5" would be the minimum for sure. I'm now waiting on a stamp to be approved for a Colt 6933 (11.5" barrel). Can't wait to pick it up.

H1 isn't a light buffer. Is that a typo?

[Iraqgunz]

This post has me somewhat baffled. For starters, I don't know why anyone would go through all of that trouble for a substandard barrel.

The second thing is something isn't right somewhere. There is either a gas leak or the port is too small. It should run with a wide variety of ammo, especially M855 and M193. Have you checked all the possibilities to ensure that you gas rings aren't worn, that the carrier key is tight and that the gas tube is good?

[rob_s]

No, I started off by ordering a 9mm upper receiver. Instead of a real 9mm upper receiver (no forward assist) as pictured on their website, they sent me a regular A2 upper receiver. I returned it, but they would only give me credit towards another purchase. Since I had been wanting a 5.56x45 SBR, I ordered a 10.3" 5.56x45 upper half, receiver, and buttstock from them (all but the LPK). Unfortunately, they had an incorrect barrel profile picture on their website. They didn't send the one pictured, but rather one that was significantly heavier. The resulting rifle was very front heavy. It took a couple of months and many calls to get them to correct this. They actually had to reprofile the barrel. After going through all of this, I just did what I had to do to get it running. The whole thing was such an ordeal that I was pretty sour by the time I got the reprofiled barrel back from them. I just couldn't stand the thought of going through anything else with them. I think that they just had more business than they could handle at the time. Hopefully they've improved their customer service since then. I need to clarify about the PRVI M193. It throws the spent brass out 100%, but the carrier doesn't lock back after the last cartridge 100% of the time.


BTW, I ended up getting a factory Rock River 9mm SBR that is awesome, so I'm happy that things didn't work out with the CMMG 9mm AR15.

Can't help but quote all of this drama and point out that this is what happens when people play fiddle-****.

All that horseshit and you could have bought a Colt 6933, gotten the same functional use out of it, and been shooting all this time instead of spending all this time on the phone and playing monkey games. I'm going to start linking every "I want to 'build' my first AR myself threads" to this post.

Henceforth this will be referred to as "Exhibit A".

[Bret]

H1 isn't a light buffer. Is that a typo?

Not a typo, just bad memory on my part. I weighed it and it's 2.94oz which makes it a carbine buffer.

This post has me somewhat baffled. For starters, I don't know why anyone would go through all of that trouble for a substandard barrel.

I didn't realize that the barrel was substandard. Gas issue aside, what's wrong with it? Also, keep in mind that I didn't go in to the transaction with the intent of buying this barrel. CMMG wouldn't refund my money, so I had to spend the credit on something.

The second thing is something isn't right somewhere. There is either a gas leak or the port is too small. It should run with a wide variety of ammo, especially M855 and M193. Have you checked all the possibilities to ensure that you gas rings aren't worn, that the carrier key is tight and that the gas tube is good?

Everything was new when I started, so the rings shouldn't be worn. They look fine, but I honestly don't know how to test them. The carrier key is tight and the gas tube looks good and straight with no binding. I guess that I can remove the front sight block and take a look. What is the size of the hole in the barrel suppose to be?

Can't help but quote all of this drama and point out that this is what happens when people play fiddle-****.

All that horseshit and you could have bought a Colt 6933, gotten the same functional use out of it, and been shooting all this time instead of spending all this time on the phone and playing monkey games. I'm going to start linking every "I want to 'build' my first AR myself threads" to this post.

Again, I didn't enter in to things with the intent of getting jerked around. I couldn't find a new Colt 6933 at the time for a decent price, but I've got one paid for now. I'm just waiting on the stamp. I've also built four AR15's including installing barrels without a bit of trouble. But, I do agree. Quality just costs more.

Henceforth this will be referred to as "Exhibit A".

If others can learn from my experiences, all the better.

[Iraqgunz]

Bret,

CMMG barrel are usually overgassed (read large ports). Additionally unless something has changed their barrels used to not be HP/MPI tested and inspected. That may have changed according to their site.

In any case it would appear that they screwed you which is too bad. Hopefully lesson learned.

Also when you ask "what's wrong with it", it should be obvious. Your SBR is not working properly. That alone should be enough of a clue.

Not a typo, just bad memory on my part. I weighed it and it's 2.94oz which makes it a carbine buffer.


I didn't realize that the barrel was substandard. Gas issue aside, what's wrong with it? Also, keep in mind that I didn't go in to the transaction with the intent of buying this barrel. CMMG wouldn't refund my money, so I had to spend the credit on something.



Everything was new when I started, so the rings shouldn't be worn. They look fine, but I honestly don't know how to test them. The carrier key is tight and the gas tube looks good and straight with no binding. I guess that I can remove the front sight block and take a look. What is the size of the hole in the barrel suppose to be?


Again, I didn't enter in to things with the intent of getting jerked around. I couldn't find a new Colt 6933 at the time for a decent price, but I've got one paid for now. I'm just waiting on the stamp. I've also built four AR15's including installing barrels without a bit of trouble. But, I do agree. Quality just costs more.


If others can learn from my experiences, all the better.

[Bret]

Hopefully lesson learned.

Well I won't buy from them again for starters. I learned from the process too which is never a bad thing.

Also when you ask "what's wrong with it", it should be obvious. Your SBR is not working properly. That alone should be enough of a clue.

I was talking specifically about the quality of the barrel aside from the gas issue. You answered that question. Thanks.