Without a bore scope probably the best you can do beyond visual appearance is slugging the barrel with pure lead. The Germans criteria was the uniformity of pushing the lead slug the full length of the bore, constant force full length. This was called bullet uniform. This is not a test for accuracy, only shooting will prove that out. But it will give you an idea as to "terrain" and measuring the slug as to overall bore dimensions. Taper or voids can be sensed by the travel of the slug.