Chamber & Cartridge Reader
Turn 12/70, 65, or 2 1/2 into a chamber length and the cartridge cases that fit it.
Chamber & Cartridge Reader
Read a proof stamp or catalogue line such as 12/70, 65, or 2 1/2. The first number is the bore. The second is the chamber, which is the longest cartridge case that belongs in it.
65 mm is 2 1/2", 70 mm is 2 3/4", 76 mm is 3", and 89 mm is 3 1/2". A shorter case of the same gauge can be used. A longer case cannot. This does not check proof pressure or steel shot.