I think "bolt bounce" is usually when the bolt closes then bounces back slightly, right? That isn't the problem I'm having, but I think my problem might be similar.
I just got a second upper for my AR. My AR still feeds reliably, but the bolt doesn't always lock back when the last round is fired. The magazine springs are okay, and the bolt always locks back properly when using another upper. This would normally lead me to believe it's short stroking, but judging by the recoil, that didn't seem to be the case. Also, the problem is more common with higher pressure ammo such as M855. The bolt occasionally fails to lock back when firing white box Winchester or American Eagle, but pretty consistently fails to lock back with IMI M855. This leads me to believe the bolt is coming all the way to the rear and rebounding off the rear of the buffer tube so quickly that the bolt catch couldn't move up into place in time. That's just a theory, I've never heard reports of that happening before. Anyway, I replaced my H1 with an H2 and the problem seems to have went away, but I would like to try and H3 and see if it will function without short stroking. If so, I'm thinking it might be better to go ahead and use it instead of the H2 (just to give a little extra margin against having the problem again). Is there any other way I can confirm that the bolt is coming to the rear to quickly? Thanks.