![]() measurement exceeds 738 thou.Ģ0 thou as minimum wall thickness is often advised as a practical minimum, but some think below 25 thou reduces value. chamber alteration) or when the bore had been enlarged by 10 thou (or more) - i.e. The gun would go out of proof from any alterations (e.g. ![]() I may not be fully up to date here - so please someone step in and correct if I'm talking nonsense! For a 12, originally proved as a 12, that would be a nominal 729 thou bore. I don't believe wall thickness is measured - only bore diameter - and that only 9" from the breech. It seems likely that 2" chambered guns, designed to be light and fast handling (as well as having lower pressures) would have been a little more thinned and perhaps to a slightly different profile - but not to the extent that they dented easily.Īs I'm sure you know, proof is about the change in dimension since last proof - not absolute dimensions. So called 'best' guns with fine balance had the barrels very carefully struck up leaving plenty of wall where the pressures were high - and saving weight where the pressures were lower - thus keeping the weight between the hands. However guns below 20 thou dent more easily and each dent removal looses a little more metal. I think it was Greener who experimented with guns wafer thin near the muzzle - without bursts. There are many factors wall thickness near the muzzle is not required so much to resist internal pressure, but to resist dents and damage. ![]() A lot of older English guns were quite thin even when new.
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