At least to me the HUGE advantage in using a 45/70 or 450 marlin comes with the intended use, velocity range it operates at and the fact that a hand cast, hand loaded projectile performs nearly perfectly and will allow you to hunt at far lower cost for ammo yet still have a very VERY effective gun that will easily allow 200 yard or a bit further, kills on game for far lower cost, plus the satisfaction you get from owning a rifle that shoots very accurately with cast projectiles you can push to near the design limitations.
I think you'll find as I have that a 4%-5% tin added to wheel weights makes a very noticeable difference in the appearance and the ability of the bullets to rivet yet remain relatively intact after expanding on impact.
you will also find dropping them into a 7 gallon bucket of water filled about 7/8 full tends to make a better quality bullet , I generally cast about 10lbs-20lbs of bullets at a time then pour out the water and spread the bullets out on a beach towel, separate the few culls and bits of casting scrap that you always get and then dry the bullets and lube size them.
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I found this bullet to be especially accurate in my marlin 45/70 over 45 grains of IMR 4198, Im not sure what velocity youll get in your rifle but cast from 95% wheel weights and 5% tin,well lubed its accurate,and it shoots thru deer,hogs and elk , holds tight groups,and generally works real well with expected results..very dead game.
you might not feel the same, but the ability to fabricate 200-500 projectiles at home on a few hours notice is a big plus in my opinion