I bought a converted SL8/G36 from IRUNGUNS a few months ago and I've been having issues with it. When I first got it, the bolt would not lock back on an empty magazine either when I manually cocked it or after firing off the last round from a magazine. I contacted IRUNGUNS and rather than having me ship it back to them, they agreed that it'd be OK if I took it to a local gunsmith and sent them the bill. The first time the gunsmith looked at it, he found that the bolt catch spring was lined up on the wrong detent. After he adjusted it, the bolt would lock back on an empty magazine when it was manually racked. I thought the problem was solved but when I took the rifle out to the range, I found that the bolt would still not lock back upon firing off the last round of a magazine.
I took it back to the smith's and he worked on it for a week or so. Thoroughly cleaned it, reseated everything, checked spring tensions, and tried a few other things but the issue still persists. It seems like the bolt is only traveling back about 90-95% of the full range of motion. It picks up rounds from the mag and ejects them cleanly, but it won't lock open. I've tried SL8 mags, Spear 5/30 mags, and a G36 mag modified to fit the magwell I have but I get the same result on every mag. The smith did notice that the pistol grip/lower is a little bit narrower than the SL8 upper and he thought that the two Allen screws might be pinching things in. I'm going to try to insert some washers and see if that fixes the issue.
Has anyone had any similar issues? Any tips on how to fix this? It's very disappointing to spend so much on a rifle and not have it function properly. I know this has been an issue for some using AR-15 mag adapters but I'm not using an AR-15 set up.
