No, it is not pinned or spot welded to the receiver. Rather, it’s threaded and secured with a bit of red locite that is easy to burn out with a bit of heat from a propane torch. I’ve done this lots, reconfiguring my couple of 590a1s (which previously wore 18.5 inch heavy wall beaded barrels) to take Mossberg 500 barrels by easily changing out the mag tubes, action bars, and forends.