Another pp ?

[jonk]

Got another question here.

I've heard of pp bullets smmothing out rough bores.

How exactly does this work? If a hard copper jacket won't do it?

And even accepting it DOES, doesn't that mean it's removing metal? Won't that wear the bore fast?

[docone31]

Paper is very abrasive. It is almost non-compressible.
Copper is a soft metal.
In all cases, contamination can occur. I shot 40 paper patched rounds through my bore, that made real shiney. I had a real rough bore, a lot of 20 went through the bore, short sized with grit. I then fired 20 with no grit.
I worked in a paper mill for years. Where the paper contacted the steel, it was highly polished! Where there was weight, the paper wore a depression. Now, this was over a period of time with little interruption.
Firing through the bore, there is pressure, and speed. Add heat, and the abrasive properties go up on the bore.
I have found, lubeing the patch slightly, the barrel does not get quite as hot for the same amount of rounds. It gets hot, but not quite as hot.
I did observe, the rifleing is now very sharp, vs., before where it was not quite so sharp.
That could have been from the barrel being real new, without having been broken in.
So, to hopefully answer the original question,
The patch is engraved into a plane. This plane keeps its shape throughout its travel in the bore. High spots will be reduced, low spots will be glossed over. Engraveing entry will get smoother. Chatter will get smoother. Paper does remove metal, although it is microscopic indeed. The tighter the fit to bore, the more pressure. Like using sandpaper, the less pressure, the less removal. Even copper jackets remove some, as the copper is also implanted on the bore.
It is called fouling.
It is controlled abrasion that paper patching produces.
My rifle has deep rifleing grooves. I can see where I can patch for quite some time before the bore is shot out. If it is micro groove, possibly I might not want to shoot a thousand rounds ever time I target shoot.
Heat is the largest factor in barrel wear. That is aside from contamination, other factors.
Heat wears the bore fast. If you cannot kiss the barrel, let it cool down!
I suspect, paper very quickly eliminates feathers, chatter, most minor imperfections. My barrel now shines real nicely. Inside looks sharp, consistant, and clean.
Heat!
The other wear factor.