.36 caliber under hammer ML. That thing had I bet a 1.5lb trigger on it, it would go off if you just THOUGHT about touching the trigger.. I used to lean it up against a tree to load it, just wasn't gonna take a chance of any part of it pointed in my direction, and sure enough, it went off against the tree, bout deafened me, but it didn't shoot me. It was a loaner, I was never happier to deliver it back to the owner!