I'm not a fan for dry firing although happy enough doing it with bolt actions with their large strong firing pins and stops. Shotguns and handguns are a different story and I always use snap caps for these firearms. Can be made from fired cases with a section cut from a suitably sized o'ring to glue in the primer pocket to absorb the shock from the falling hammer.
Nylon in a snap cap on it's own is not much better than snapping dry, nylon inserts need springs behind them to absorb the firing shock.