It is noted some rather extensive testing was done many years ago in England. A pressure barrel was fitted to a pendulum gun so recoil, pressure & velocity (Observed over 20 yds) could be measured simultaneously. A single barrel was used with two interchangeable extensions for a total length of 30". These two extensions were very precise fit with the bores lapped in to that of the barrel's bore, one being a true cylinder & the other carrying a full choke,
Choke of course had no affect on the max chamber pressure but was included to assure all loads fired were of regular ballistics. Various levels of loads were fired using several variations of powders available at the time.
Two things stood out in these tests, one the full choke gave a consistent higher velocity over the 20yds. Tow the full choke gave slight but consistent "Lower" recoil. It is well noted that higher velocities with lower recoil are not normally compatible.
Explanation Please!!
