I seriously doubt that the blow back loosened your scope mounts. They probably weren't anchored well enough at the start. If there was just a tiny bit of oil in the screw holes or on the screw threads, they will come loose. These areas need to be degreased with alcohol or some such. A spray can of carburetor cleaner or brake cleaner works well. Put some clear fingernail polish Or loc tight) on the threads, re-tighten them, and give the gun another try.
You can eliminate much of the blow back by adjusting your breech plug. Screw it in all the way finger tight, then back it out 1/4 turn. Put a fresh primer in and see if you can close the breech.
If it does NOT close, screw it down a tiny bit and try again. Keep doing this until it closes tight on the primer.
If it does close, back it out a tiny bit and try again. Keep doing this until it will not close. Then screw it down just enough for it to close.
You'll probably still get a little blow back under the scope, but not much. Put a piece of black electrical tape or duct tape on the bottom half of the scope where the blowback hits it. Problem solved.
