The rifle is a Bushmaster QRC. Took it to the range today, and here's what happened: Locked the bolt open, inserted a mag and let the bolt go back into battery. Pulled the trigger and heard a click. Tried to open the bolt with the charging handle and it wouldn't budge. I don't know whether there's a round in the chamber, but I don't know why there wouldn't be. With a great deal of difficulty, I pushed out the rear take-down pin. The rifle wouldn't swing open. Removed the pivot pin, but the top and bottom wouldn't separate more than a fraction of an inch.

I was able to see a little into the receiver, and it looks to me like the buffer jumped its retaining pin and is jammed up against the back of the bcg. I thought maybe the best way to get it apart would be to remove the buffer tube and get to the buffer and spring from the back, and hopefully pull them out of the receiver.

But I can't get the tube off. I turned the castle nut as far as it would go. Slid the plate as far back as it would go. When I try to unscrew the buffer tube at moves a little and then stops. It feels like it's being stopped by a pin or something that needs to be    moved to allow the tube to unscrew.

That's where it stands now and I don't know what to do other than asked you folks for help or, that failing, call the factory. Any help would be very much appreciated.

Thanks,

Mike

Hammer's sticking up in the middle of the bolt carrier, jamming the works.

Should be able to separate the halves by tugging almost directly UP and a little bit forward.

Buffer, if it's jumped the detent, will spill out of the stock with its spring, but that's not a big deal.

Once you have the halves separated, you can work on getting your lower set back up properly, and levering the bolt carrier out with its stuck (potentially live) round, using hand tools.

Try "mortaring" the bolt open. Put that bitch back together, then simultaneously pull the charging handle back while you pound the rifle stock straight down into the ground. Few good raps like that should get it open. Maybe a rifle primer popped out jammed the shit up.

If you have a collapsible stock, make sure you collapse it before mortaring. For real.

First thing that popped in my head as well outside it being a primer only because he said he got a click (no round fired). Was this the first shot taken or were you able to shoot it prior to having this issue? Definitely reassemble everything and give the mortar technique a try. It usually solves most stuck case malfunctions even if your buffer retaining pin sheared off.

Maybe that broke retaining pin if binding up something as well. Can you confirm whether that's indeed broke or not?

I had the same problem about a week ago, buffer retaining pin and spring had jumped out and were lodged in the bolt. If I remember right I pulled both pins and separated the halves, it took a bit of wiggling. You should be able to unscrew the buffer tube, it might have some loctite on it or the castle nut has been staked.

Buffer retainer pin should only contacts the buffer when the receivers are open. Sounds like the rifle didn't go completely into battery, (bolt not seated in receiver ext).
If the buffer over road the pin, you have some serious problems.
Also sounds like you have a live round loaded. Mortar while pulling the charging handle as said earlier. Stay clear of the muzzle. Good luck and keep the crew posted.

It's got nothing to do with the buffer, or retaining pin.  You have a round in the chamber, and it sounds like it's slightly out of battery (is there a gap between the bolt carrier and barrel extension visible in the ejection port?)

As already mentioned, use proper and safe technique to 'mortar' the round out of the chamber.

Sounds like its out of battery. I've have a round or two lock up in partial battery pretty hard. I've gotten lucky and been able to pry the carrier back from the front of the ejection port, mortar technique if I can't get anything in to pry with.

One problem solved and another revealed.

Two slams with the mortar technique did the job, and a live round was ejected. I took out the bcg, inspected everything including the barrel extension - it all looked fine - and I put the carbine back together. I dry-fired a few times. It worked fine.

I put a live round directly into the chamber (safety on!), let the bolt go forward and it would not go into battery. I pulled on the charging handle to eject the round and it was locked up tight again. It took the mortar method to open it. I tried a few more rounds -some singly fed, others magazine fed - and had the same problem with each. Had to use the mortar technique each time. I was using Federal American Eagle ammo which is the only thing I've used in this carbine. There were no marks on the cases when they were ejected.

I examined the bcg, the charging handle and the barrel extension with my amateur eyes and didn't see anything that looked unusual. I'm thinking it must be a problem with the bolt and/or the barrel extension, but I don't know that. I appreciate the help you've all given me up to this point. I'm hoping you can bail me out once again.

Thanks,

Mike

That's sounding like short headspace, if not an outright wrong chambering. Especially considering it's factory loaded commercial ammo you're trying.

Send it back, if you can, otherwise, it will require at least polishing, if not re-reaming of the chamber, to get anywhere, I fear.

Take a look in the chamber, see what it looks like.  Could be half a shell in there.

separate the upper and lower and function check the bolt closing and engaging the gas tube

Problem solved thanks to MisterPX, who suggested I check the chamber for a (partial) obstruction. Looking down the barrel from either direction showed no blockage. I put a round in the chamber to check again whether the round was seating properly in the chamber. It was not going fully into the chamber. The round wouldn't fall out on its own. When I pushed it out with a cleaning rod, guess what came out with it? A patch! It must have been hiding in the neck of the chamber so it wasn't visible looking down the bore. The rifle is functioning fine now.

Lesson learned. Actually, two lessons. The patch and the mortar technique.

Thanks, everyone, for your help.

Mike

Glad it worked out!

OH wow. Be glad that patch didn't make its way farther down the bore. That could have been ugly.

Lot of headache for cleaning mistake.

Wow.  

Glad it worked out.  Sometimes it's the little things.