Problem with LWRC PSD upper 556

[steaminwilly]

When fired the bolt blows back in the buffer tube and gets stuck. I have to completely disassemble the rifle/lower to get it apart and try again. Happened twice in a row. I am using a Seekins lower with a Geiselle SSF trigger. Not a full auto gun but just the SSF trigger.
What the hell is going on here?
Thanks in advance.

 

[pepito]

When your Upper arrived, did it come with a new buffer spring? Is there an excess of play between the upper and lower?

 

[steaminwilly]

It did come with the buffer and spring, which I installed. There does not appear to be too much play between the lower and upper, but I'm not sure what is too much/too little. I threw on a KAC upper and it ran fine.

When fired, the BCG extracted the round then got stuck 60% in the buffer tube and 40% in the upper. Couldn't move it back any further with the charging handle and I couldn't bang it forward. I had to remove the trigger pins and jimmy that sucker out. Pain in the ass.

 

[KNIGHT11B4]

Is there a mark or small hole on the rear portion of the buffer?

Every once in a while a screw or something in the rear of the tube will stick too far into the buffer tube and catch the nonmetal material on the rear of the buffer. Not sure which stock you are running but worth checking.

 

[steaminwilly]

Its a KAC buffer tube, no screws or anything at the end.
Thx for the help fellas!

 

[chainring]

Well...if it wasn't NFA I'd say to run it on another lower and see how it runs. Sounds like the LWRC carrier doesn't like the KAC/Seekins build. Does it cycle by hand OK?

 

[steaminwilly]

It hand cycles fine. I'll try it on another SBR lower