Sanded or cheesegrated bondo? One or multiple coats?

Personally I do not think bondo would last in the primer pocket long with the force being imparted on it. Bondo, I feel, would be too brittle, and if it lasted longer than one striking, would surprise me. I would expect nice blue pieces of sweet smelling paint cracker being stuck on the face, the water table, the breech, and probably falling down into the bore after firing with bondo filled primer pockets. It just sounds like a recipe for a mess to me.

While I loate fiberglass filler from an automotive standpoint, I could see it surviving the impact caused by a trigger pull much better than bondo.