Success! I finally have loaded rounds that fit my chamber. The RP brass worked. I seated my bullet using the dummy round from SSK and it fits perfectly. I loaded some testing rounds and hope to shoot them tomorrow. Fingers crossed.

As a side note, SSK said Blackhiils Shooter Supply has tons of RP 444 Marlin brass. I called and they do, BUT they don?t sell retail. So, it can be tricky to find readily available Rem. brass.