I have recently become the owner of a 1919 (found by Serial number search on this website) Field Grade 20bore sbs in the UK. The barrels are clearly stamped with 70mm for the chamber length. The barrels are also marked as "Armor Steel". I have quite happily been using 2 3/4 (70mm) shells of 24gm 7.5 shot size for clays. The shells are made by Lyvale Express and have a muzzle velocity of 1400fps. Having read your responses to chamber sizes, has the age of my gun been correctly identified? Should I be using a lower shot weight, say 21gm? And finally, could I use a larger shot size say 5 or 6 at 21 to 24gm loads for hunting