Would firing steel jacket bullets smoothen a rough but clean bore better than copper/guilding metal jackets that will just fill the pits?

brownell's sells lapping bullets which depending on rough the bore would help.

No, steel jacketed bullets are not much harder than copper and won't help you. If your bore is truly rough, you need to lap it with a lead lap and lapping compound. Read more on fire lapping with bullets before you do it. Lots of opinions on both sides of it.

Yes, BUT...

As you observe, steel is a bit tougher than copper and less likely to deposit. Less, not none at all.

Firing any bullet wears the bore. How many you got? Mil. surplus. Those 7.62 Russian bullet would wear in a .308 bore...

To speed this wear up, some coat the bullet, lead and jacketed, with a grinding compound. I believe I saw "valve grinding compound" mentioned in one article.

You want to be very, very careful. It is very easy to wear the bore too much and if it gets "loose" then you lose accuracy too.

As suggested, look up "fire lapping" and study long before you proceed. Not too difficult but ??? your call. Happy Trails.

Generally valve grinding compounds are much too coarse for shooting through barrels and are made of carborundum which is much too hard, being right next to diamonds on a hardness scale.

There are commercial compounds available which use much softer grinding media (which does not imbed as much in the bore, and breaks down quicker) and have much better (finer) grits.

Generally speaking you want nothing more coarse than 200 grit for the first few shots through a VERY rough bore, perhaps 140-280 grit for a moderatly rounf bore, and 400 grit for the final polishing shots.

I prefer the kit sold by NECO, which has three different grits from course to fine and a very complete instruction booklet. There is a good selection of other kits on the market too.

Holley crap man just go get some JB bore cleaner and bore bright