Bladesmith, we have had this conversation before. I think an enterprising chap with funds at his disposal could buy the necessary equipment and set up a voluntary USA proof house and for a fee of about $30 per gun would make a fortune and make guns like the ones we are discussing "in proof". I have an inkling though that lots of you chaps wouldnīt want to put your BP proofed fine old guns through nitro proof which I understand. If the barrels are good use them with black but John above is exactly right on the insurance front...in the UK or Europe if you fired a nitro cartridge though a non nitro proofed shotgun and injured yourself, well, thatīs your bad luck. If you injure someone else you are certainly sued for an enormous amount (we learnt that from you chaps wink ) and would also go to prison