Originally Posted by Durangokid
Many orginal Brown Bess Musket over 250 years old are in shootable condition. These guns have fired tons of lead balls and are not worn
out. These were not patched rounds.
Durango, your comparison is ill-fitting, play on words intended.
A shotgun slug is designed to obturate, to seal off, the gas pushing it from being wasted and passing around it. The metal slug itself, or parts thereof, uniformly engage the barrel especially at the choke which, if there is any, swage the always softer-than-steel lead alloy. With me so far? Rifled slugs are actually big minie-balls of a sort, and the rifling lands are actually more there to reduce friction and optimize swaging.
A Brown Bess (let's call it a Short Land Pattern or even 2nd Model) on the other hand had a bore considerably wider than the diameter of the ball. All smooth bore military muskets used this feature. Why? Blackpowder guns foul. Fact. With a tight fit the ball would have to be rammed and soon the gun would be unfireable, the gun inoperable, and the soldier less useful. A loose ball could fall down even a somewhat dirty barrel and be pushed gently the rest of the way to safely fire, cleaning some of the fouling out on the way, and the soldier stay in the shooting-match all the live-long day. Benefit. In theory. And practical it was for its time.
Of course it made the Bess less accurate as the bullet was going in different directions depending on the last part of the barrel it happened to rattle off of last on its way down the tube towards the enemy. That's why you could pretty safely stand 100 yards away from a single Redcoat. If they bothered to take carefual aim at you (which was not
part of their doctrine and hard to do without a rear sight anyway) they were not going to hit you. No wear to speak of in any case.
A shotgun, on the otherhand, will always have a microscopic amount of wholly insignificant wear with a slug. My guess is the OP's friends are concerned the powder charge is really nitro-glycerine and the slug is a solid billet of industrial diamond 'cause it didn't come out of a factory. I am not justifying their decision but I might understand it...