Gentlemen, you are wandering off track when you talk about firing smaller than proper caliber rounds. While the brass may look dramatic, you do not have a pressure seal in the barrel, which is required to burst the chamber. Probably don't have a good seal at the breach face either. If the bullet was lead, you might cause some lead to be smeared in the rifleing by flame cutting as the hot gasses blow past the undersized slug. This might be a problem with later shots with proper size ammo.