Is the ML the regular Staghorn, or the Staghorn Mag?
It is theold StagHorn with the two piece barrel/receiver. It is good for only 100 grains of Pyrodex. Those old StagHorn guns have a 1" in 24" twist barrel. Maybe that is why it shoots the 370 grain Maxi-Ball pretty good. i also have a CVA Magnum Hunter. Got to try it out with the 370 grain Maxi-Ball.
BTW, forgot to mention that i did use a TC bore button under the Maxi-Ball.