Well Doug . . . all of this remains in the "unknown" category, until someone does something like firing a 3" shell in a 2 1/2" chamber and seeing if the velocity increases vs a 3" shell fired in a 3" chamber. Both Sherman Bell and Arthur Curtis (the latter reporting in an American Rifleman article from 1936) did indeed fire 3" shells in 2 1/2" chambers--Bell in a 12ga pressure barrel, as part of his "Finding Out for Myself" tests, and Curtis in standard .410's with 2 1/2" chambers. Both reported blown ends on the shells. Bell reported the nearly 1500 psi increase in pressure. Neither, unfortunately, provided comparative velocity readings. Bell would not have noted increased recoil, since it was a pressure barrel rather than a shoulder-fired gun. Curtis reported no "trouble or great discomfort other than would be expected from the use of high-speed loads", and he apparently didn't bother to shoot the same 3" shells in a .410 of the same model, only with the appropriate 3" chambers, so that he could make an on the spot comparison of recoil. But we do have other reports of increased recoil from long shells being fired in short chambers, and while one would tend to say--given the major factors in how recoil is generated--that it must be due to increased velocity, we don't know that for sure without velocity measurements having been taken. On the other hand . . . with a blown end from the shell also going down the barrel, we have now increased ejecta WEIGHT vs the same shell without the end blown off. So that might be a possible explanation for a noted increase in recoil. Although not a lot of additional ejecta weight . . . who knows? Certainly easy enough to test for a velocity increase, using a .410 with 2 1/2" chambers, if anyone is willing to do as Curtis did and fire 3" shells in one of those.

Food for further discussion and experimentation . . . and truly unfortunate Jim Legg is no longer here to join in on the discussion.

Last edited by L. Brown; 11/27/11 07:59 PM.