There is an article in HANDLOADER number 217 that you really need to get a copy of. Written by Brian Pearce, it explains the different power levels the .45 Colt can be loaded to, in different strength guns.
Basically, it says a model 25-5 has the exact same strength cylinder as a model 25-2, 625 (same thickness walls, materials etc.) and therefore is safe with loads that go up to 23,000PSI. That is the same pressure as .45 ACP +P loads generate, and S&W rates their model 25 variants chambered in .45 ACP for +P loads.
If you go to John Linebaughs websight,(the man who practically wrote the book on the .45 COLT) you will find all kinds of technical info on the 25-5/.45 Colt. He goes as far as 30,000PSI for a rating, while still keeping a 100% safety margin that is a requirement of his.
You can get a back issue of Handloader number 217 from Wolfe Publishing. Go to their web sight and I believe you can order it there. I simply called them and ordered it. It is by far the best article I've ever seen on the .45 Colt in 40 years of reading gun articles.