Earlier, I posted some thoughts on a .357 revolver/rifle (S&W's, Rugers & my Marlin 1894S), and thought I'd add my work with a Ruger .44 Magnum Flat Top 40th Anniversary Blackhawk, my Marlin 336 in .44 Magnum and my son's Marlin 1894 Octagon bbl'd. .44.
Both of the rifles performed very well with a variety of jacketed bullets, both Remington 240 gr JHP's as well as Hornady's excellent XTP's in 200 & 240 gr weights. All three bullet types did very well in our .44 handguns's too. (3 Ruger .44 Special Flat Top BH's, the aforementioned .44 Mag Anniversary BH, two S&W M29's, and a S&W M69 and M629. The loads listed below will do less than 2" or a bit better at 100 yds from the rifles, and less than 1.5" at 25 (from a rest) with any of the handguns.
If you're into cast bullets, the Marlins can be a bit more demanding. I use my own cast LSWC's fitted with annealed Hornady gas checks and size them all to 0.432". Cast from an alloy of air cooled wheel weights, with a pinch of tin to help with mold fill out, I use 50-50 alox/beeswax lube and have no problems getting great accuracy, and no leading even with Marlin's Micro-Groove rifling. Herco or Win 231 are good powders with Lyman's 429215gc at ~225 gr or 429244gc at ~250 gr. With either powder, 8.5 gr is a superb load doing as well as the best of my efforts with Hornady XTP's. BTW, Marlins reportedly, can have feeding problems with LSWC's, as well as with overall cartridge length, but these two, GC'd cast bullets feed just fine through through our guns.
These two cast bullets, sized 0.432" do equally well in all of our handguns, showing no signs of over pressure, and producing groups that run well below 2" at 25 yds from a rest. Throats in the short guns run from 0.430" to 0.432". We've experiences no significant leading with the wheel weight alloy, and the 50-50 lube. Lyman's 429215 GC with 8.1 grains of Win 231 gives me 1045 fps from the 6.5" Ruger Flat Top Magnum and an estimated 1400 fps from the rifles.
In our guns, with the jacketed bullets listed above, especially Hornady's 200 gr XTP, we've had great success with 18.5 grains of AA #9 for ~1600 fps or 23.5grs. of Winchester 296 for 1750 fps with the 240 gr Hornady XTP. Either is a first rate deer load on our KY white tails with the long guns and an authoritative load in the handguns.
As always as, these are my loads, checked with both Lyman #49 and Sierra Infinity manuals, and I've found them safe in my guns. If interested you should consult your manuals, consider the pressure implications and work up to them slowly.
Best Regards and HTH's, Rod