I began using H322 in an old original modern Marlin around 25 years ago. I shot a lot of cast bullets (Lyman 385 grain RN) in that shallow groove rifle. The only problem with using those bullets was that they tended to tumble. Many loads/powders were so bad that you could hear the bullets 'bumblebeeing' as soon as they left the muzzle. The first and only powder I found that would shoot them stably was H322. And it doesn't seem to be particularly fussy about mild, moderate, or heavy loading either; many ways to get useful loads with it.
