03-13-2023, 03:07 PM
Try some 20-50 ( 20-40, 10W30) synthetic oil on the bolt carrier, lubed up well on all areas that make contact with the upper. Shoot one shot at a time to test for complete bolt lock back. Might take 100 rounds or so to "wear" enough to function. If no joy, then other items as listed above need to be checked/addressed.

