Hand loading ammo is a great and learning experience! As many know, most of the first “magnum” cartridges – and many new ones as well – have a “belt” near the rim of the case which we are told helps to properly head space the cartridge, because the belt stops the round from going any farther into the chamber. Many “experts” consider this a better and more solid method than head spacing on the shoulder of the cartridge, especially those with sloping shoulders, since the force of the exploding powder charge might compress the cartridge farther into the chamber than desired.
The .300 Savage round pictured has been modified to head space on the shoulder much more securely than on a normal sloping shoulder. In a properly reamed chamber, it would be nearly impossible for this round to go father into the chamber than it is intended to. It is expected that when fired the main body of the case will expand to the diameter of the “collar” on the shoulder. Whether or not this will prove to be a major advancement in metallic cartridge technology, it definitely proves that reloading dies in the hands of less than experienced users can sometimes do strange and unexpected things!