Alk8944 has given you good advice. I use 2400 to load for my .38-44 Heavy Duty revolvers, but they are N-frames, and built for it. I have used it in .357 for my Rossi Puma carbine, and it excels there. Tried a couple of those in my M13-2, and recoil was vicious, primers flat, and extraction a little stiff ! I don't do that anymore and don't recommend that you do. With a 158gr. lead bullet in a K-frame, not more than 10.0gr, and never less than 6.0. Light loads of slow powder seem to be a bit iffy. hth

Larry