A couple of years ago the Birmingham Proof House were having an abnormally high percentage of failures in 20 bores. Not choke damage but just burst barrels and cracked actions as would be expected from proof overloads. I don't know if Smallbore has any knowledge of this. I submitted a 20 bore with damascus barrels at around that time. The barrels were o.k. but the action was bent like a banana. Lagopus.....