While I don't have the Marlin, my 375 WCF is a Winchester (top eject) "Big Bore"; I purchased it from an old hunter from Maine about eight or nine years ago.
He used it on Moose, Bear and Deer in Maine and Canada; he preferred the factory 250gr load and the rifle was sighted in for that when I got it.
I have used RL7 and IMR 4198 with 200gr Sierra, 220 Hornady and 255gr Barnes "Originals". So far 18 hogs and 3 whitetails have been turned into tablefare.
As a general observation, the 200gr Sierra is softer than the 220gr Hornady, the Hornady has exited on broadside shots and several quartering shots; the results were all terminal, no follow up shots were needed and tracking was easy (Stevie Wonder could have followed the blood trail)to non existant.
I have yet to kill anything but milk jugs with the 255gr Barnes, not too much bullet upset, but 5 milk jugs gave thier life for the cause. I loaded some for a bear hunt (the bear wasn't on the same song sheet that week).
Mine will go to deer camp again this year, it's a great rifle for sneaking around in the tamarac swamps.
Have fun with your Marlin 375.
