I used to have one, great guns. Stick to loads for the Colt SAA & you will be fine. A 255gr LSWC @ 900fps is even enough for deer out to 50yds. If you want to hot rod an Nframe, get a 44mag.

The online place for S & W info is the Smith & Wesson Forum, they have a handloading section on the forum. I can tell you that +p loads are not recommended for the 25. You should remember that the N Frame was designed for the 357 magnum in the 1930's. The cuts on the cylinder for lockup are underneath the cylinder on a Smith. Therefore, the cylinder wall is very thin on a .45 caliber. It will not stand up to +p loadings very long.
If you want a gun to 'hotrod' get a Ruger. In my opinion, there is nothing as fine as Old style "pinned and recessed" N frame. Take care of it, you have a treasure!!

A while back I did read some stuff on that gun at either sixgunner.com or one of the links off of there , it might have been some of John Linebauh's(sp?) stuff ? but the guy was getting away with extensive use of some pretty warm Ruger-like loads .

I think one of the Smiths would work OK with a cast 300gr flatnose at around 900 to 1000 fps and that would give you some pretty good thump .

These are some of the most practical field carry guns ever devised. S&W had a program a few years back in which they would modify the throats at no cost. You might pursue that. I have casted 260 gr. SWC with a soft base and a hard nose with a slight heat treatment(only the harder front takes the heat treatment) for several years and they work great. remember the limitation for the M25...this load does allow the base too upset minimizing the throat issues. For full power buy a Ruger Bisley, and load 325 gr. LBT bullets at 1300 fps....it will do more than you can imagine until you witness it. Skip the 5 shot conversions the extra power is not worth the trouble unless you just want one like I did. ged