Colt 6721 not cycling PMC

[rj1974]

I have a Colt 6721 that will not cycle PMC bronze the LWRC M6A2 and the Bushmaster run it just fine . The Colt will cycle anything else I put in it but with the PMC bronze it will eject but not come back far enough to strip a round out of the magazine . I put new gas rings on it even though the felt fine and the gaps were staggered , Im thinking get a lighter buffer .

I read a few different places that the PMC bronze is loaded a little light . Anyone else have any issues with it ?

 

[browning guy]

I think you have a bad rifle just give it to me and I will take it off your hands.

 

[rj1974]

I think you have a bad rifle just give it to me and I will take it off your hands.

OK , Ill trade you my broke AR for your old worn out 1892 Winchester

 

[clandestine]

Common problem. First a lighter Buffer, then a lighter Recoil Spring. The black ones JoeBob sells are about 10% lighter than Colt Factory Buffer Springs.

If that don't work then it could be an issue with the Gas Key or worse off the Gas Port is just too small.

 

[rj1974]

Common problem. First a lighter Buffer, then a lighter Recoil Spring. The black ones JoeBob sells are about 10% lighter than Colt Factory Buffer Springs.

If that don't work then it could be an issue with the Gas Key or worse off the Gas Port is just too small.

Between playing with the 3 rifles , the buffer in the Colt definitely has more resistance then the LWRC and BM . Picked this one up for my son so I want to get it running right for him .

Looks like I'm off to JoeBob's to see if he has any in stock .

Thanks

 

[browning guy]

Hail Lord Chad !!!!!! Another problem solved!! he is like a Doctor that makes house calls

 

[clandestine]

Between playing with the 3 rifles , the buffer in the Colt definitely has more resistance then the LWRC and BM . Picked this one up for my son so I want to get it running right for him .

Looks like I'm off to JoeBob's to see if he has any in stock .

Thanks

If you can pull a BCG from another proven AR and try it. Just to eliminate possible BCG Issues.

 

[rj1974]

If you can pull a BCG from another proven AR and try it. Just to eliminate possible BCG Issues.

That I can do .

It was just with the PMC bronze , I ran 4 other brands/types through it the same outing and they all ran fine in it .

 

[clandestine]

That I can do .

It was just with the PMC bronze , I ran 4 other brands/types through it the same outing and they all ran fine in it .

If it does it with PMC it will likely do it with steel cased ammo too. Not sure if you use that though.

 

[rj1974]

If it does it with PMC it will likely do it with steel cased ammo too. Not sure if you use that though.

No I only run that in the mini14s

 

[TopTechAgent]

I have a 6721 and some PMC bronze but haven't run that through yet. Will try and see if I have the same experience. Thanks all for the advice in the event I need it as well.

 

[bigjohn]

my RRA came with a spring that was too heavy to run the lower powered rounds. swapped it out for the brownells replacement spring and a 9mmm buffer. works great now

 

[Lou45]

AFAIK, Colt buffer springs are primarily made for 5.56 pressure loads and are a bit heavier than some other manufacturer's buffer springs. The heavier spring helps keep the gun from getting "beaten up" from 5.56 loads, especially under heavy rapidfire and/or full auto conditions. Using the lighter spring with full power 5.56 will cause the gun to suffer unnecessary abuse internally from the BCG being slammed to the rear. If you want to run lighter loads, the lighter spring will be fine as Chad has indicated. But if you want to run full power 5.56 again, be sure to go back to the heavier spring as it will absorb the shock and prevent the unnecessary amount of slam.

 

[jrumann59]

I have a spikes that does not like PMC bronze, so far the only ammo it won't take. From what I understand PMC bronze is a little underpowered and can cause cycling issues.

 

[kbarrett220]

Is your rifle MILSPEC?

 

[jrumann59]

Is your rifle MILSPEC?

Mine is, I built the lower and bought a complete upper. I am going to try swapping the BCG with a NiB one I have in one of my other rifles.

 

[ObsceneJesster]

Just change your buffer out. You're Colt probably has a H2 or H3 buffer and the Bushmaster probably has a Carbine buffer. I almost promise you that if you swap the buffer out of your Bushmaster and into your Colt, the Colt will cycle all of the low powered crap your Bushmaster has been cycling.

 

[ObsceneJesster]

I have a spikes that does not like PMC bronze, so far the only ammo it won't take. From what I understand PMC bronze is a little underpowered and can cause cycling issues.

Does your Spikes have one of their T2 buffers in it? Check the buffer and if it says T2, H2 or H3, then just swap it out for a carbine buffer and it should cycle lower powered loads.

 

[TopTechAgent]

As a follow up: today I had a chance with my 6721 to shoot the PMC Bronze. No problems at all on my end, it fed just fine.

 

[rj1974]

I took the upper and another proven AR to the range today . The other AR runs them fine so I swapped uppers and the Colt upper still would not run them . I swapped the BCG out of the proven upper and into the Colt upper and it ran them just fine .

So it is time to look at the BCG , it already has new gas rings in it (brownell's).