Do note that upon the introduction of the fold crimp, just prior to WWII the British began experiments with shells longer than the chamber. They were mostly halted by the war but resumed immediately afterward. From that point onward virtually all British 12 gauge shells marked as suitable for 2˝" chambered guns were actually put up in a longer hull.
Bell brought this to the attention of a lot of shooters, but to be totally correct in giving credit where credit is due, he neither Discovered it nor Invented it. This fact had been long settled likely before Bell ever pulled his first trigger.
I don't know just how old Bell is but in less than a month I'll be 81 & this was all "Laid to Rest" before I turned 12.
It was certainly discussed in British literature, although mostly forgotten on this side of the pond. Gough Thomas' "Gun Book" includes a chapter called "Danger in Case Length", which dates from October 1964. Burrard made reference to the same thing earlier than that. The Thomas article even includes a test he arranged to have run by Ely, firing 2 3/4 shells approved for guns with 2 1/2" chambers in test barrels chambered both 2 1/2" and 2 3/4". Pressure was measured in tons per square inch (standard Brit measurement at that time) at 1" and 6" from the breech, and observed velocity (average over 20 yards, also Brit standard at the time) was also measured. 10 shots were fired in each test barrel. Differences in both pressure and velocity were minimal between the two test barrels.
