Looks like I'm pretty late to the party here but in your second picture of the jam it appears that the bolt carrier, not the face of the bolt, has stripped the round from the magazine. You may still have a gas issue or something is preventing your bolt from traveling fully to the rear. I have experienced this with a build of my own (coincidentally also a Gibbs receiver- AR15 side charger and also using a JP silent capture spring system.... Additional specs: 20" Lothar Walther barrel with match bolt, Noveski nickel boron BGC, Geissle SSA trigger, Tactical innovations Lower, PMAG30 magaizines). Opening the gas port slightly larger than spec. for the cartridge (.223 wylde) and installing an adjustable gas block resolved my issues and also allowed me to be able to tune my cycling for different loads while being able to adjust for any overgassing issues. It now runs as well as any of my factory rifles. The action is smooth and I have had no cycling issues with any factory loaded ammo since the modification. It should be mentioned that I only run quality name brand ammo through the rifle and have a mild affinity for Hornady varmint rounds for this one but it really likes 40gr Noslers in my hand loads.
The point is, if Gibbs inspected the rifle and the only thing they found is that they were able to resolve the cycling issue by enlarging the gas port in the barrel then I'm sure they adjusted it only far enough to cycle reliably with the ammunition they were testing with. I'm sure they would have told you if you assembled something improperly or were using incompatible components. They have no reason not to tell you that you twisted the action during installation of the barrel nut or that the BCG is causing your issue, etc. You may want to research gassing solutions or find a smith with experience resolvong the issue before assuming that Gibbs has built an inferior product. My experience is that I really like my Gibbs receiver once I figured out what my issue was and it has become one of my favorite rifles.
