I've shot .357Mag at 300m with great lack of success - undoubtedly you'll do better than I did shooting your Low Wall and its lovely long barrel by comparison with my 8.375" S&W. Loads in that for 300m were not comfortable in a handgun, but would be just fine for a rifle.

Since I'm not in the business of posting reloading data here based on my own experience, I'll let you look up the details, but I WAS shooting a 170gr gas-checked hard cast rather than a FMJ - see post #13.

Lead seemed to work better on steel than FMJs - maybe its was an illusion, who knows?

tac