.357's are SB1 frames as are .44's. If you want an SB2 frame, they come available, then just buy or have factory fit what barrels you're interested in. BC .45-70 and Colt are SB2's and any std. rifle calibers since 1987 if memory serves came on SB2. The .357's have been Maxied I believe on SB1 without issue. Sure others will chime in.