I'd go with the .358 but slugging is never a bad idea. I prefer buckshot or cast round balls over fishing weights. A simple whack with a hammer on an anvil should make a good slug from a .36 ball, maybe even a 00B pellet.
Life Member NRA, TSRA
Smokeless powder is a passing fad! -Steve Garbe
I hate rude behavior in a man. I won't tolerate it. -Woodrow F. Call Lonesome Dove
My favorite recipes start out with a handful of used wheelweights.