Deffo the TC bullets work very well in the Marlin and although the RNFPs chamber fine no one I know can get them to be accurate.
I use a very light load - 2.7 grains of D0302 (similar to Bullseye but cleaner) and a minimal crimp which delivers about 770 fps - fine for target work up to 50m
Have always used .38spl cases at .38spl COL with no porblem. It will need a good clean if you switch to 357magnum cases but if switching from lead to jacketed bullets you will anyway have to get all of the lead out first - jacketed bullets do not push the lead out of the barrel, they push it into the barrel wal - I ruined a barrel doing that.
I get the idea with .357 brass but it is so moch dearer than the 38spl (actually I have a lifetime supply of 38spl brass from my pistol days).
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TANSTAAFL