Drew, thanks for posting the photo for me. The crimp closed aluminium 12 bore cartridges are 2 1/4" when fired and contain 1 1/8th. ounce of shot. The 16 and 24 bore ones are also 2 1/4". The 12 bore ones on the right are 2 1/2". I once owned a Belgian .410 shotgun with the chamber length marked on the Proof Marks as 63mm. which equates roughly to 2 1/4".
Some German made shotguns I have encountered have very sharp angled chambers and I can only think that it was done to accommodate a true 2 1/2" paper roll crimp case that when fired would give a seamless transition of the shot from cartridge to bore. 2 1/2" being 65mm. it is considered safe to fire a 67mm. cartridge in these guns but the sharp chambered German guns will chew off the end of the case a bit and leave it ragged looking. Lagopus.....
