For slightly pitted bores, I have lapped them using a expanding slug and fine valve grinding compound. It smooths out both the lands and grooves. It is time consuming but I believe offers better control than fire lapping. I did this on a schuetzen and was able to shoot 1/20 cast bullets very accuratey afterwards.

I first lightly oil the bore.

I put a chamber guide on a cleaning rod and then screw a 2" long all thread into the cleaning rod. I then wrap the rod below the all thread with a greased patch (greased cotton string will work). I put a nut on the all thread.

I insert the rod from chamber end into the bore to the all thread protrudes slightly from the muzzle and then and cast a slug around the all thread.

I push the slug out about 3/4 the way and butter it with fine valve grinding compound and slowly pull it in the bore for a couple of strokes. The chamber guide needs to be kept tight in place to keep the rod centered. The barrel is then turned horizontal in the vice.

After a few strokes, I push the plug out 3/4 way and rebutter it. When fully in the bore, retighten the nut to press tge slug outward.

I have screwed a second rod (with rod guide) onto the all thread at the muzzle. This allows all strokes to be pulling strokes. Pull from the chamber end until the slug is at the chamber and then pull from the muzzle end with 2nd rod.

I usually spend most of the time working all but the last 2" of the bore. This gives a slight choked bore.

Needless to say, this is somewhat time consuming but I have taken somewhat dark bores and make them shine with nice lands and grooves.

Now if the bore is deeply pitted, it is time for a rebore or relining or just use jacket bullets and hope for a small pattern.