KC, I just had another thought regarding your Marlin's feeding problems. Bullet nose shape can be fairly critical in a lever gun, just like a semi auto pistol. Your .30-30 feeds so well in part due to the bullet shapes it uses. Stubby, blunt nosed revolver bullets can present feeding problems.
I'm a big fan of the old Keith style semi-wadcutter in my revolvers and have, at times, tried to make them work in my lever guns. Quite unsuccessfully. The sharp edge at the front of the first driving band seems to thwart all efforts to make these feed properly. I have had better luck with bullet designs that incorporate a more rounded nose profile, and no secondary shoulder at the front driving band.
These feed well:
These don't:
Granted, these are from bullet molds (from Lyman and RCBS, respectively), but many commercial lead bullets, and even jacketed bullets, share features of these designs. Look for bullet shapes that more closely mimic the upper one, and maybe that will help.