I asked much same question several months ago and got various suggestions. Initially, I used some "scotch tape" which worked will for a round of sporting clays. Then I cut a shim from a thin Al can and that has been in place for at least 6 rounds of trap and is till keeping barrels on face and will be repeated as needed. At some point I will have a local gunsmith solder a thin peice of metal (shim stock) onto the hook -- expected cost under USD100. This shim stock will have a few holes in line along its center to allow excess solder to flow into them, giving a good, tight fit of shim to hook. For hunting and a few tens of rounds of trap per year, this soldered shim is expected to be totally adequate for years. The gun is a 1890s Husqvarna hammer double with early fluid steel barrels.
Niklas
