I just swapped out my upper for an aero precision one and am now having a problem.

When i pull the bcg back, the carrier will move but the bolt gets stuck in the chamber. Ill release it allowing the carrier to go forward and close completely and on the second time trying to pull the bolt back it will release. Ill drop the bolt and same thing. First pull back stuck, second attempt released.

I never had this problem with the bolt getting stuck on the previous receiver with the same barrel. It was always smooth.

I did the following checks:
     Made sure gas tube not the problem - nope
     Tried a different BCG in the gun - no problems
     Cleaned and clp'd the problem bolt - no effect
     Cleaned chamber - no effect
     Tried problem bolt on another gun - no sticking problem on other gun.
     Tried different charging handle - same thing
   

Im lost on this, as there was no problem between this bolt and barrel on the old upper, now there is.  

Any ideas or suggestions as to why it is now getting stuck on the first try when i pull back and releasing on the second try??


Thanks guys

Interference between the charging handle and the new upper?

Does it cycle correctly when fired?

Check the feed ramps on the barrel extension to make sure they aren't slightly misaligned. The index pin might be bent or sheared.

Swap out the cam pin on your bolt with a known good one.
It might be out of spec.

Are you sure the tail of the BCG isn't hitting or catching somewhere on the receiver extension/buffer tube?  Try cycling the bolt with the upper removed from the lower. Does it still catch on the first pull?

Yes i did try it without the lower attached and same thing.

Could be hanging on the forward assist.

What did you figure out, OP?  Everything working now?