Welp, you could reload w/ black powder, I suppose...
I shoot my 1858 Remington .44 w/ 30-35 grains of Pyrodex 3F, that's a 140-ish gr. round ball @ probably 900-1000 fps. That puts it in .38 spl territory, muzzle energy wise (with an admittedly larger hole on each side!). Of course , the fouling is so bad that I think I'm going to save up for a Kirst converter!
Found this on the cast boolits forum (not my load data, use at your own peril!):
Uberti Cattleman 5.5 barrel
357 Mag brass
168gr SnakeBite bullet (Black Powder Bullet)
22gr/v of Goex FFF
Est Velocity - 774 fps@223ft/lbs of energy
Again, somewhere in the .38 spl range.
I suppose the questions would be, what bullet are you using, how much space does that leave in the case, and how much compression would you put on the load?
Could you do it? Sure. Would it be a pain in the butt? Absolutely!