my first trip to John Gallagher's shop, he showed me one of his .458-400 vaqueros in six shot configuration. he said the max that the gun would safely take was a 400 at 900 fps or somewhere there about. it was his Alaskan backup bear protection. he said at the Linebaugh seminars that this combo only gave up around 6 inches of penetration to the 475 linebaugh at max. playing with my 45 colt with the max cylinder cut down to fill up the window, it doesnt do well on the chronograph until bullet weight gets to 340 grains minimum. seems like my 45 should at least reach 900 fps and maybe a little more with 400 grain class bullets. doesnt seem to me that 0.006 of an inch should make that much difference in stability and what not. i am thinking that it is most likely rifling twist. maybe GlennS will chime in. what say ye?
matt