the best results I ever got from my 444 marlin when I owned one was from the hornady 265 grain jacketed bullets over a max load of IMR 4198 but
to be fair the 295 grain NEI was also a good projectile
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my marlin had the micro groove rifling, the later versions may be more accurate with cast projectiles
but I found the 45/70, 450 marlin and 458 lott and 458 win are just better suited to use of cast projectiles than the results I got from the 444 marlin, that in no way suggests it won,t work, because it does and does well, but the 444 marlin twist rate won,t stabilize the heavier projectiles as well as the 458 caliber bores in my experience.
everything I tried in that 444 marlin i owned that weight over 320 grains was not particularly accurate past about 150 yards.
you generally have no issues with a 350-420 grain cast projectile in most 458 bore rifles, many larger case cartridges will allow fairly high velocitys over 1800 fps with a 400-420 grain, something you can,t do with a 444 marlin

and while your free to disagree I think the 450 marlin caliber BLR is a significantly stronger and more accurate cast bullet rifle choice

Last edited by 340mag; 05/04/15.