I am a cartridge guy, however 5 yrs a go I acquire muzzle loaders ( Rem 700 ML and CVA Optima all using 209 s.shell primers on line ) to benefit of longer hunting season, also some area only allowed M.L or s.gun.
At start I use Pyrodex pellets 2-50 gr with 300 gr. hornady or T/C hallow points 45 cal with plastic sleeve to fit the 50 cal bore.
Good results on target and every deer either drop dead on the spot or within 30 yds, but found them very dirty, lot residual and long to clean.
Change to Triple7 pellets also 2-50 gr. equally good results an paper and on game, maybe same or little less residual with the difference that clean much faster.
Since I always clean the rifles the same day I use it at the range or as the hunting is over, I do not notice any corrosion signs.
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roberto