For your other question about the bore size I would ask if you have any bore size lead conicals? If you do, then I would suggest you use a hammer and bumpone of the conicalson one end to swell the diameter to around .520 or so. Then start the bullet into the barrel from the narrower end of the bullet and push it through the bore. This will give you a slug to measure both the lands and grooves of your bore and if desired, you could send it to the bullet supplier and have them size the bullets based on your bore slug. This also gives you a chance to check the bore for uniformity i.e. loose or tight spots in the bore.

REAL bullets can also be used for this as long as the bullet slightly exceeds thegroove diameter.

Good luck.