Here is a problem I have found recently in Brit land concerning readymade cartridges especially if used in older 2 inch chambered 12 gauge guns. In the picture of the fired cartridges you can see that there is a length difference though on each of the boxes they were recommended for 65 mm or 2 inch chambered guns. You can see that the blue case top is feathered by friction because it has entered the forcing cone and in doing so increased the recoil and more than likely the service pressure also. My conclusion is that some older guns have chamber lengths of exactly 2 inches while others are a little longer giving some leeway. The black case is manufactured by my preferred maker Hull Cartridge Company the other longer case by ELEY number two on my makers list.
