I personally like cast bullets in the 125 grainish range using fairly moderate speed propellants, and just came in from shooting some test loads. I was using GI brass, Lee 124 TL TC bullets sized .358" seated 1.070", WW primers and various propellants. You can get some dandy subsonic loads using the bullet I mentioned. For example from my Beretta M9:
4.3 grains of Power Pistol avg 997 fps
4.2 grains WW231 avg 1067 fps
I usually go with 4 grains of WW231, but wanted to see what it took to get at the threshold of trans-sonic. Both of these were extremely consistent, well stabilized, accurate from what I could tell, and very minimal leading even with it's less than smooth bore. This bullet using water quenched WW's will weigh about 129 grains.
4-4.2 grains of Unique is a very good subsonic load, and if stepped up to 5 grains gets me 1183 fps. Final load development using INTERNATIONAL CLAYS works out to a comfy max of 4 grains which yields 1128 fps. Lots of fun, dirt cheap shooting here, that sacrifices nothing and functions the pistol 100%. Of course these are my loads, and are safe in MY pistol... Use at your own risk.