With a conventional bullet it is easy to crimp them in place with either a taper or roll crimp. However with a heel bullet since the bearing surface is the same diameter as the case mouth, they cannot be crimped in the usual way. This crimp die (not a full die set) is designed to crimp heel bullets. The case needs to be loaded and the bullet seated and then this die will apply a firm crimp to the case mouth. As the cartridge is pushed up into the die it applies pressure to a collet that then compresses onto the case mouth, crimping the bullet into place. These are set up for Bertram brass cases (0.900″, Mk I) however, they are adjustable and can handle brass of different lengths. This is ideal for 476 Eley/Enfield bullet that we carry.