Years ago, I picked up a M71/76 Mauser Carbine, in .43 Mauser chambering, of course.
The early guns had very deep rifling, with .436" bores and a .457" groove diameter, for .0105" deep rifling, each side. A .446" paper patched soft lead bullet was shot in this era round with 77gr. Black Powder. The fast-pressuring black powder charge efectively obturated the bullet to fill the rifling, and produced reasonable military accuracy - 4" at 100 meters about normal. One must remember this bolt actioned rifle was way ahead of it's time and metalic centreally primed ctgs. were quite new. The Model 71/86 had a .446" groove diameter and .436" to .437" bore.

The bore of my rifle was very rough - like a rusted sewer pipe.

I wanted to firelap the barrel, but since the chamber's neck wouldn't allow a bullet large than .446" to be seated in the case, I rechambered it to .450 Alaskan, a wildcat on the .348 Winchester Case. This allowed the use of full diameter bullets and allowed me to firelapp the barrel.

Long story to the result with lead bullets. I rolled the bullets to impregnate 20 grit valve grinding compound into the full surface of the bullet as both lands and grooves of the bore were very rough.

I loaded these rounds with a very light charge of fast burning smokeless powder to produce a speed of 1,000fps approximately.

After firing 40 rounds of these fire-lapping loads, the bore diameter increased to .437" and the grooved iameter increased to .458" - both measurements a full thousanth of an inch larger than prior to the test.

The bore now shines one end to the other, although it's still a bit rough from the odd deeper pits. The important thing here, is the pits are no longer sharp edged, but rounded and the barrel doesn't lead. It's shootable and will hold in 3" at 100yards with the battel sights on it's short 20" barrel.

Sometimes, abrasion is a good thing. The loader is in control of what goes out the tube.