I recently acquired a Marlin 336 in 44 Magnum. When I slugged the bore, the groove diameter was .433. I had some jacketed 240 grain bullets at .430 so I loaded a few just to see. Haven't shot them yet but don't have high hopes. My 44 molds throw bullets at .433 so I'm not thinking it's going to work well with any cast bullets I have
Any one have any advice?