I shoot hard cast and gas checked 30-30 rounds from my Win '94, not micro groove.
I also shoot hard cast and gas checked .444 from my micro-groove Marlin. When shopping for a .444, I researched 6 ways from Sunday, because I knew I was going to almost exclusively shoot cast rounds from it, and through my research was dead set on finding a .444 with ballard (1:20) rifling, but I just couldn't find one. Main reason what that in .444, micro-groove has a hard time with bullet stability above about 300gn. I am testing many rounds in the 240 - 300gn range, and having a lot of fun, but I know there are some projectile moulds out there that are 350gn and higher that I'd be interested in trying, but might not unless I can find a sampling somewhere instead of buying a quantity. I have no leading problems with any of the cast rounds I am using, with any of the loads I have experimented with - I'd done light loads and lobbed projectiles, and I have also approached max recommended with a few powders, all are shooting fine. I do have some jacketed rounds that I got on a good deal, and they shoot great, but before I switch from copper to lead (or vice versa) I clean the barrel.
I do not know this as fact, but based on the above, I might suggest that the only real problem you might come across is a ceiling weight for your projectiles for them to remain stable. I'm sure there are those with more knowledge and experience than I who will chip in.