Dear SBR owners

I´m having problem with couple of short barreled uppers, 11.5" Bushmaster and 10.5" no name upper. Guy who sent this 10.5" upper to me told  it is Wilson barrel and it has been reamed to 5.56 NATO chamber.

At the very moment I got this 10.5" in my hands I first checked the headspace, it is OK no problem here.

11.5" is almost new Bushmaster and it has been bought as a rifle or at least the owner told me so.

Problem in both are very same very bad FTEs.
I tested them with South African surplus and IMI M855, so ammo is not the issue.

Now, SBR owners or anyone who knows, I would like to know what to do before I drill gas ports bigger.

Another thing I would like to know, could anyone of you specialists explain me what is "bolt bounce" in layman terms.

Thanks in advance,
MN

My 11.5" CAR had a problem with FTE's also. Seems the extractor would lift over the rim and not extract the brass. I just put some heavy wolffe extractor springs in with the little buffers (which can be purchased from Georgia Precision). I also installed a new heavy CAR buffer spring to slow down the bolt a little. Not had any FTE's since that cannot be directly attributed to the ammo (neck sealant etc.)

TAC40, thanks for the input.

Luckily I happen to have one Wolff extra power recoil spring but I will use it as last resort. I´m also planning to make heavy buffers by turning solid brass inserts to standard buffers.

To be exact, the ejection problem does not occur as extractor slipping over rim but it´s "dropping the case" inside the upper receiver before ejector throws it out and causing severe jams.
Ejector springs are std. power but good condition.

More info welcome.

MN