Not a damascus, but here's a Krupp barrel that's .018" wall at the start of the choke. Bulge became noticeable after about 200 rounds, 100 per barrel, of 1 ounce 6500 psi loads. The so-called gunsmith didn't follow what we agreed to on max diameter for honing. Bores are now .738" and choke diameter at the muzzles are .712 & .713". Not a lot of constriction.
