Cheif,
You'll find that Marlin has at least .002" constriction under the rear sight dovetail, a .001" or greater constriction under the roll engraved warning and lettering on the left side of the barrel, and perhaps a slight constriction where the slot is milled in the bottom of the barrel for the barrel-band screw to align. Lap these out, and the gun will shoot like gangbusters.
Charlie's got the right idea regarding bullets, shoot what your gun likes and go hunting! Although we have large, heavy critters up here in N. Idaho (Griz and Moose), the truth is that Elmer Keith and friends did about everything this planet had to offer with a 250g bullet in the .44 Magnum. I tend to like bullets over 250 grains but the simple truth is this: In all these years of making and marketing our bullets, I've only had three confirmed reports from customers (at least that customers have told me about) of .44's 300 grains and under being recovered from game in the lower 48 states. Two of those were on hogs, each of which were found (by different customers) after the bullets had totally penetrated the target hog, and lodged themselves in their second piggie victim... which also expired!
When you think about it, the odds are, that even using our extremely efficient 265g WFNGC you'd hunt a lifetime of real-world scenarios and never recover a bullet.
Slug that bore, and see what's going on with the constriction issues, and too, see if the .432's that you've loaded up don't shoot much better than what you've been playing with in this gun.
Please, give us a report.
God Bless,