32 S&W Long with crimp that can resist extreme recoil
32 S&W long [.920" 15kpsi]
32 H&R mag [1.075" 21kcup]
327 Fed Mag [1.200" 45 kpsi]
And I do shoot 327 Federal loads in my 32 S&W Long 100 year old Colt revolvers... with beefed up forcing cones. I can get 1413 fps with HNDY 85 gr bullets. But I leave the chambers alone, as the cylinders are so short that I can only use a 1.3" OAL, and I have had to build special tooling to get the right crimp at that length.
I have converted many of my 38 specials to 357 magnum.
To convert a 38 to 357 I put a .380" straight fluted reamer into a chuck, put some cutting oil on the chuck, and with a few twists of the wrist, each chamber in the cylinder gets converted. I use an empty case as a chamber gauge, and then cut a hair more.
Here is the .380" reamer for $33http://www1.mscdirect.com/CGI/NNSRIT2?PMAKA=02033801
For 327 Federal, I would probably use a .334" straight fluted reamer. That would be SAAMI sloppy, so if you want tighter, you would have to research your range of ammo diameter near the case mouth.