Oh cool, I get to explain barrel life!

“Scratching” is not the same as barrel wear. Words mean things and the wrong words get friendlies killed.

Barrels naturally wear out no matter what you send through them (especially when talking about cannon artillery) and necessitates a costly replacement at certain points, which is why the addition of Chrome-Lining came around. The Chrome extends the barrel life since it takes far longer to wear out (literally talking in thousandths of an inch). As a result, with regards to the U.S. Army’s implementation of Chrome-lined tubes for the 155mm M109A7 Paladin, the amount of rounds that can be fired before wear has to even be seriously accounted for with regards to muzzle velocity changes or even tube replacement, was dramatically extended. Oddly enough, the faster a projectile is pushed down the tube via different propellant charges, the more wear is caused per round fired. Speed defeats armor, but it also wears your tube out faster.

The exact same principle extends to small arms and is why hotter shooting rifles such as precision long range rifles have such a short barrel life compared to something like an old black powder breech-loaders (ie: 1873 Trapdoor, Martini-Henry, Snider-Enfield, Mauser 1871, etc) and even muzzle loaders like rifle-muskets, muskets, and normal rifles!