Yep, I've checked all of the 357 rounds I have, they all fall just short. And the regs read "As rated by the manufacturer". So I assume hot hand loads are iffy, as they cannot be rated by the manufacturer. It seems that the 44mag (maybe the 41 mag, haven't check it) is the smallest widely produced handgun that is most always legal method of take.

Also, you would have to find someone with published ballistics in the longer barrel, like the Corbon. Most rounds are rated at a single barrel length, and may be hot enough in a long bbl, but if they never get rated that way... might have to do some extra convincing to the DOW.