I recently purchased this gun and not knowing anything much about them, I've been learning a lot. I have found out that it has British Proof marks on it. on the top of (I guess it's the bolt?) there are the markings: 7 tons with a square beside it, .45, .900, BMP with a crown i think. The Bmp is on the slide and the frame. There is no designation that it's not English made like I've read some have. I read that the 7 tons is the proof pressure in psi. I have also read that it's not a good idea to shoot factory modern ammo in these. I have shot a few Lee 200gr rnfp in it over 4 gr Clays. That load should be in the 15,000 CUP range but I can't tell for sure. Starting load is 3.6 gr for 11,000+ CUP and max is 4.3 gr for 17,000 CUP. Is this safe in this gun? I thought proof loads were stiff loads that were much more than the recommended everyday load. The way I read this, 7 tons is 14,000 psi and this a proof load? I don't want to blow this old gun, (or myself for that matter) up!