I have shot several thousand rounds of 140 gr bullets over 16.5 gr of 2400 back in the 70's when I was "searching" for the right loads....I ran a lot of those thru a 4" 65 and they were "intense"....as post #14 mentions....each and every gun is a different entity....having worked with thousands of different guns in several dozen platforms over 40 years as an instructor I can testify to that.....and as the previous post discusses 2400 in shorter bl's.....I use 2400 in 6" bl for magnum loads and then go to Unique in 4 or shorter.....burns more efficiently, does not have the tremendous muzzle flash or report that 2400 does in the shorter tubes....as pointed out by Bob in the above post...when running max loads, it is always a good idea to do that for each and every gun you are going to shoot them in. I have had some revolvers that digested one load just fine, then load that same load into another revolver and have the primer flow back and lock up the gun.