Drew,

I was under the impression that under English proof law lengthened forcing cones was considered a "material alteration" as are the installation of choke tubes & requires reproof but a quick search this AM does not confirm that on the lengthened forcing cones so I stand corrected.

Stan,

For the record I'm not advocating the US adopt a Proof Law, all I'm saying is that in countries that do have a Proof Law it would make sense to address alterations & repairs to both the interior & exterior of the bbls which the existing English Proof Law does not effectively do by only considering bore enlargement over original
proof diameter & not taking lost wall thickness due to restriking & or refinishing into consideration.