Look more like tool-marks caused by the gun drill or the reamer picking up swarf and scoring the bore before rifling. Insufficient coolant / lube pressure out of the cutting head of the drill or reamer will cause this.
Trying to lap this out will excessively enlarge the bore diameter, and you have already noted some muzzle wear.
Just get as much fouling out as you can without removing barrel steel and start again. Stick with FLAT-based bullets of approx 174-180gn.