Bill I had a 375 big bore years ago, ran it full house with soft lead gas checked boolits, shot ok at the time - but ok then woulda been 4 - 6" at 100yards with the barrel sights - I was recoil soft those days and that thing booted - I sold it and when the 38/55 came along (nice wood, 24"inch octagonal barrel) I bought it. That gold plated piece sat on the rack with a box of ammo beside it for almost a year - I would take it down, oil it, put it back in its place, it came (supposedly) new in the box, unfired, I walked in there one lunch time and like it was mocking me from on high, grabbed it down with three rounds and a paper target, out the back and at 50 yards off a rest those three almost touched.
So now youre not unfired !!
A couple days later I shot a string of ten at 100yards my rest that day was a woven plastic fertiliser bag with a few shovels of dirt in it - stripped the gold plating off of the sharp edges on the underside of the action ----oooooops!
So now youre not New In Box anymore
Lets see can we make a blackpowder shooter out of this ?
Its one of the few Lever rifles I have seen that stays right on point as it hots up - a well made gun and a fine shooter (just a shame about the gold plate - blue finish woulda been better)
I just use that LEE 250 grain PB boolit, FFFg powder, one juice box wad over the powder, homemade blackpowder lube (50/50 beeswax and neatsfoot oil)
for yours I would forget the powder coat for blackpowder - its a hindrance - takes up space that would be better filled with grease lube