My M2 20ga has a mount and if I mounted anything heavier than a light red dot, the mount loosened under recoil. I have recently custom shortened longer screws that are lock tited (red) into place. Now I have 100% tread contact and I am hopefull it holds. The screws that come with the #93 mount are too short.
My backup plan is to source some threaded inserts that are coarse threaded for aluminum with plenty of locktite. the inside of these steel inserts will have normal mount screw female threads. this is the system Browning uses on their gold 10 ga NWTF models. I have not found these inserts with just a little looking, but they should be available.