I am being told by some that english guns are a different breed and that they are generally very thin.. Is this the case? the gun I am referring to is a holland.
Many (most?) English guns have been designed for light weight and fast handling. The barrel walls are made thin where pressure allows to reduce weight and improve balance and handling. With suitable English loads (which tend to be lighter and lower pressure and shorter cases than many American loads) they are as safe as any gun. Wall thickness requirement to survive the pressure varies down the barrel - peak being near the front of the chambers, and being much lower at the muzzles. Generally - barrels can be very thin at the muzzles from a pressure point of view, but would dent very easily.
20 thou towards the muzzles would be considered adequate, but will dent easily. However, much more is needed nearer the chambers. It is impossible to put an exact figure on this and expert advice should be sought if there is any doubt - and any advice given, particularly in respect of cartridge type and performance should be followed carefully.
Where an English gun is 'in proof' (i.e. not excessively enlarged in bore, pitted, altered or damaged since the previous proof) it will normally be safe FOR THOSE LOADS AND CASES FOR WHICH IT WAS PROVED. For many English guns that will be 2 1/2" cases and light (by American standards) loads.
