Larry, I was quoting from Wirnsberger on the 12/C and 12/LC rules. I have a W. Betts pigeon gun with 12/C, three inch chambers, and proofed for 1 1/2 oz and marked 3" on each barrel flat. It was made in the 1920s, I think. One often sees British guns, especially Greeners, chambered for 2 1/2" shells and 1 1/4 oz of shot, but I don't think I have ever seen 2 1/2" chambers proofed for 1 1/2 oz. of shot in a British gun.
Englehardt seems to be wrong according to examples like above. Also have a Cashmore Nitro marked 12/C and and "3 inch cases". Have a Greener Monarch Imperial marked 16/C and "2 3/4" case". Both of these markings seem to contradict Englehardt as you quote him.
Daryl, I don't believe there's any contradiction there--assuming your guns date from after 1925. From then on, the chamber length was a required marking. Since yours all have the chamber length marked, I'm guessing they all date from that later period. The 12 over LC was no longer used after 1925. Chamber length stamped on the barrel flats, if you don't have a SN chart from the particular maker, is a good way to separate 1904-25 guns from those proofed from 1925-55.
