WRONGO! Just do a search for RBCD ammo, and check out their claim of 77 grs at 2450 fps, in a 5" 10mm. If I didnt' cast for the .45, and couldn't shorten .45 Win Mag cases to fit the 1911 mag, I would invest in a 10mm! That RBCD load is 1050 ft lbs, and you are NOT going to lose more than 100 fps by using a 4" barrel. It probably isn't even all THAT hot, since several of the 10mm's in production lack fully-supported barrels. I just cast zinc slugs for the .45, and get the same slug wts and veloctities, without giving up the cheaper, more available mags, brass, bullets, etc. I suggest that anyone who fires hot stuff out of a 1911 look into drilling and tapping 2 opposing holes thru the frame, and use the protruding ends of 2 small setscrews to better hold the MSH (mainspring housing) in the frame. 1911's are notorious for "tearing out" the weak spot just below the MSH's retaining pin. The 2 screws relieve the stress on this area.