I also agree Roskoe. However I am not a gunsmith, but I've done most of the smithing on my own weapons and for many other folks over the years.
I happen to have an abused CVA Mountain in 54 cal that has a barrel that's on it's way out. Not because it's shot out but because it was horribly rusted when I obtained the rifle and I had to polish out the bore quite a bit to clear much of the rough areas. Since, I have easily a couple thousand rounds through that bore. It still shoots ok, but the accuracy is not as good as it could be were the rifle cared for in the first place.
I also have yet to shoot out an ML bore. My first ML (a T/C Hawken 50 Cal caplock kit) is 36 years old. I don't have a clue as to how many PRB's and conicals I've tossed down the bore. Tens of thousands? Not a clue. I've also shot all sorts of powders and countless pounds of 2FG and 3FG through that old T/C.
I switched to largely 3FG powders about 12 years ago.
It still shoots just as good as the day my Uncle and I put it together 36 years ago. The bore and the rifling are still clear and crisp.
Now if you
don't properly care for your ML, you will be lucky to get 200 rounds out of it.
m2c.
Tahquamenon