Perry;
As I recall Burrard's writing on the subject it was the late 30's & much of the work was delayed by a little mis-understanding between the Brits & the Germans. The primary reason for testing to see if the fired length of the shell could be lengthened while retaining the standard load was the fear of the shorter overall length of the standard length shell being closed with the pie crimp being confused for a 2" shell & loaded in a gun chambered for that length. When I first became interested in the Shotgun in the mid 1950's the Federal shells are the only standard gauge shells (.410 is not a gauge) I recall as still being loaded with a roll crimp & they advertised a Frangible top wad which was supposed to shatter upon firing, thus not "Blow" the pattern, a factor of course highly advertised by those using the fold crimp.
