I wouldn’t use anything heftier than a cast 250 at around 1200 FPS. With any of the slow burning pistol powders, specifically #2400, that shouldn’t be too hard on the gun. If you prefer jacketed, a 240 gr JHP or JSP should be about the same. If it was my own gun, I’d probably use loads in the 900-1000 FPS range, which are plenty for me in a 4-inch gun. Keeping the gun clean and limiting fast double-action shooting will help to minimize wear and tear, too. JMHO.