Might I suggest you put up a piece of dry wall and stand off 15 feet and fire it with your #6 shot. Do not put anything that you value behind that piece of drywall.
Just as an aside, I've had chats with guys re: guns and stuff over the years here but just to let you know I'm from a military family (home schooled) with some LEO's thrown in here and there. Just about every time we have a BBQ the chatting goes from music to planes and eventually guns ... all sorts of scenarios ... my last birthday the folks bought me a Ruger Mini30 ... added to my Marlin .45 carbine and my M1 .30 carbine. We hunt, we shoot.