I would need to ether dig a whole and also have a bullet stopping roof on it or build a four berm range. I was thinking the better way to test it would be to hand load some rounds with the same powder load and bullet weight (needed to cycle the action) but with a bullet equivalent that is not capable of much penetration (like a fine lead powder).

I think I would start with 2 rounds and the firearm fixed in place (to test if the action will cycle at all). Then go to oven with gun on baking sheet and 2 rounds. Then go oven rack and 2 rounds. And then maybe baking sheet and full mag if it all worked as theorized. I don't think you need a way to pull the trigger since the firearm while heating is inherently in an unsafe condition, you would have to instead leave the thing to cool for a long time (also to rule out hang fires) and unload the rounds for inspection (not to be reused).