There is one point in this that seldom gets mentioned. As mentioned, of course the load itself must be suitable for the gun in question. The British ran extensive tests on this just prior to WWII when the fold crimp shells were introduced. It was felt the normal 2½ case with the deeper fold crimp might be mistaken for the 2" shell & loaded in these ultra light guns, so extensive testing was carried out with cases of longer length. Remember that prior to this shells were closed with a roll crimp which shortened the case by only about 1/8" when loaded. The 2 3/4" case when given the roll crimp gave a loaded length almost identical to the 2½" roll crimped case. When the same load was fired from the two differeent cases both ballistics & pressure were found to be virtually identical. In spite of both Gough Thomas & Sherman Bell totally misquoting Burrard he covered this very well in his book "The Modern Shotgun". Bell's quote of Burrard appeared to be a carbon copy of Thomas, to the point I don't think he "Read Burrard for Himself" but cited Thomas. One other thing of note was, "A shell should never be fired in a gun in which the ""Loaded Length"" is longer than the actual chamber depth. A restriction of the crimp being forced into the forcing cone can delay it's proper opening & indeed can raise pressures. The point which was "Misquoted" from Burrard was his recommendation not to fire a normal 2 3/4" "Roll Crimp" shell loaded with the heavier 1¼oz charge with accompaning heavier powder charge in a 2½" chambered gun proofed for 1 1/8oz loads. With this I totally agree. Note also most American 12ga dbls were chambered for 2 5/8" cases, 16ga for 2 9/16" ones. The 20ga was chambered in 2½" length & if from a maker which adhered to the 1/8" short chambering then it is very closely approaching the length of the loaded shell. It needs a little clearence between the crimped case & the beginning of the cone for proper opening of the crimp, & I don't care what Bell said, he didn't even test that. I do shoot proper loads in shells longer than the chambers within those parameters. Since my shells are all loaded to serve as hunting loads in whatever weather should be at hand, I don't load below 7K psi even for twist or damascus.
Miller
