A 357 magnum in a rifle is a fantastic cartridge. And it is an extremely inexpensive rifle to practice with. Personally I would shoot a cast bullet in the rifle. Go with the largest weight bullet that the action will function flawlessly with. One problem I have seen with the Marlin over the years is that they sometimes have functioning problems with the heavy for caliber bullets. But hopefully yours will handle the 180's. And there is nothing wrong with the 158's.

I also like the 44 magnum as the poster above stated. But I do not think you will have any problem with the 357. Take advantage of cast bullets, and shot the heck out of it. The practice will more than make up for any slight deficiencies the cartridge "might" have. Tom.