I've got a crown protecter like this one on my short starter
http://www.cainsoutdoor.com/shop/item.asp?item=1870
Maybe I should be but I am not at all concerned about damaging my bore with a brass jag. What concerns me more is breech gases accelerating to a few thousand fps when the bullet exits the muzzle. Any way, most bore erosion occurs right where the bullet seats over the powder. The area where the pressures are highest and the seal of the bullet less than ideal. One would call that the throat of a highpowered rifle barrel but I don't guess that term applies with a muzzleloader. I figure that I'm not going to live long enough to wear the barrel down with my jag
. After over 400 rounds, I don't see any wear near the muzzle (or anywhere else in the bore).