HELP: wrong AR-15 buffer?

[Fobjoe]

I went to a gun shop in San Diego yesterday to buy a carbine buffer and spring for my UBR stock. At first they didn't think they had one then magically pulled one from a box of spare parts behind the counter. I was excited, paid $25 for it and brought it home. Installed my UBR with the buffer and thought it was all good. Noticed today that my bolt won't lock back. I measured the buffer and it's 3 5/8". A buddy of mine compared his 3 1/2" buffer. What do I have? I'll try and return it but we'll see what happens...hopefully there won't be a problem.

Anybody want to explain to me what I have?

[NiteQwill]

What is the stamping on the head?

[frigginchi]

Should lock back with an empty mag inserted.

[supermario]

Maybe its an A2 buffer? Somebody with knowledge will chime in soon.

[NiteQwill]

Maybe its an A2 buffer? Somebody with knowledge will chime in soon.

It's too short to be an A2 buffer and it doesn't have a shoulder like rifle length buffers do.

[mydogsmonkey]

dont UBRs have their own specific buffers?

[NiteQwill]

dont UBRs have their own specific buffers?

No, just the proprietary tube.

[CHS]

That looks a lot like a 9mm buffer.

Weigh it; is it more than 5oz?

When you shake it, can you feel the internal weights move around, or is it solid? That would also point to the possibility of being a 9mm buffer.

A carbine buffer should only cost 10$-12$, not 25$ (unless you were looking for an H, H2 or H3)

[kf6tac]

That's the carbine-length buffer that comes with the AR-57 uppers sold by 57 Center (www.57center.com). Their site claims that the buffer is only 3.5" long, but mine measures 3 and 5/8 as well. I don't have a regular AR bolt on-hand to compare, but my guess is that the AR-57 bolt is shorter to accommodate that extra 1/8 inch.