BCG Issues

[Oldmandan]

My barrel seems to be clocked slightly off, enough to where my JoeBobs BCG won't go into battery. The Bolt hits the barrel extension. It's only a small amount, maybe 1mm, but still enough for the bolt not to engage. The feed ramps don't line up either by about the same amount.

I've tried all 3 of my Ice arms BCG's and they all fit the PSA upper, but barely. The teeth? on the bolt are not centered, their far left and ride the wall of the extension.

I put the Joebobs BCG in a different upper (Anderson barrel) and it fits perfect

So... problem solved right? I don't know... How important is it for the teeth on the bolt to be centered in the extension, can they be riding the wall of the extension? Will it wear in over time? I'm worried it's going to shear the teeth off first time I take it out...

I have a headspace gauge en route from Brownells, but I don't think that has anything to do with it, I think its the barrels locator pin was machined slightly off.

I'll be shooting both these rifles for the first time in 2 weeks.

[CWM4A1]

I assume the barrel is already mounted in the upper receiver. Bolt lugs should not be hitting the barrel extension as it goes in. The issue might be index pin on the barrel extension budged with excessive torque when barrel is mounted. Don't think this has anything to do with headspace. I would have someone take the barrel off, check and re-mount it.

[Pryde]

I assume the barrel is already mounted in the upper receiver. Bolt lugs should not be hitting the barrel extension as it goes in. The issue might be index pin on the barrel extension budged with excessive torque when barrel is mounted. Don't think this has anything to do with headspace. I would have someone take the barrel off, check and re-mount it.

It is impossible for the extension pin to budge from excessive torque to the point it would cause this. The index slot in the upper only allows for a couple thousands on each side and that would not equate anywhere near to a significant amount of twist. What it sounds like is that the barrel extension is out of spec, this is not easily fixed and I would return that thing to where it came.

[THT]

It is impossible for the extension pin to budge from excessive torque to the point it would cause this. The index slot in the upper only allows for a couple thousands on each side and that would not equate anywhere near to a significant amount of twist. What it sounds like is that the barrel extension is out of spec, this is not easily fixed and I would return that thing to where it came.

I've seen damaged indexing slots on upper receivers because when the muzzle device was installed, it was torqued too hard and a barrel clamp wasn't used. The result was a deformed indexing slot and a barrel that was cocked to one side and out of alignment. The bolt would crash into the extension when closed and would never go fully into battery.

[Oldmandan]

I doubt PSA will take it back since I sold off the handguard and cut the sling swivel and bayo lug off (it's s dissipator, that stuff looked stupid on there). I guess I'll take it apart and have a closer look at the index pin

[m16]

I've seen damaged indexing slots on upper receivers because when the muzzle device was installed, it was torqued too hard and a barrel clamp wasn't used. The result was a deformed indexing slot and a barrel that was cocked to one side and out of alignment. The bolt would crash into the extension when closed and would never go fully into battery.

Yep.

I've seen barrel extension pins that were almost sheared off as well as damaged upper receivers from people wrenching on permanently attached muzzle devices.

Give a monkey an armorer's wrench and ANYTHING is possible.

[Pryde]

I doubt PSA will take it back since I sold off the handguard and cut the sling swivel and bayo lug off (it's s dissipator, that stuff looked stupid on there). I guess I'll take it apart and have a closer look at the index pin

Even if that's the case they should still take it back if the extension truly is f'ed up. That would mean it was defective from the factory. Never hurts to call and ask.

[Oldmandan]

I took it apart last night and went through everything, and I think I found the problem. The slot on the upper receiver that the index pin fits into is too wide, it allows the barrel to overclock when it's tightened down.

I had a spare Joebob's blem upper receiver I picked up a couple weeks ago. I put that on there and the index pin fits much tighter now. Hardly any play.

I inserted the BCG that previously wouldn't fit, and it now goes into battery. The Ice Arms BCG fits even better, it's just a gnats ***** from being centered. I feel much better about shooting it now.

Unfortunately, I'm out an upper receiver. Although I can probably make it work on a future build, now that I know what's wrong with it. A little wedge between the index pin and the upper would fix it.

[m16]

You could always send it to Randall @ ar15barrels and have him drill the barrel extension pin hole slightly larger so you can use a pin that fits the slot in the upper.

[kkp]

A decent gunsmith (such as Randall) might be able to fix it/remount it properly. Probably worth the money to save an otherwise perfectly decent upper.

[isplice]

If you want to try to fix it yourself, buy a cheap combination set of feeler gages. Find the right size to shim one side of the pin so the barrel clocks right. Then trim the gage so it slides into the slot and re-install the barrel.

[Oldmandan]

My PSA upper looks like it will be fine now, since I replaced the upper receiver. It just kinda sucks to have to redo all this.

I'm also building a 9mm AR, so I'm thinking I can use the out-of-spec upper receiver onto that rifle since the the 9mm barrel doesn't need to index anywhere. It uses a freefloat handguard, so the indexing won't affect the front sight either.

It should also be mentioned, PSA's website says they test fire all their uppers prior to shipping. I call BS on that, my upper came with the lo-pro gas block clocked 1/8" to far to the left. I don't see any possible way for this thing to pass their QC if they had tried to test fire it.