The Super Kurz

[Nelsdou]

Quite some time ago I embarked on a quest to wildcat an 8mm “Kurz” following the lines of what the Germans did with developing the 8x33 Kurz from the 8x57. My idea was to come up with something more powerful than the 8x33 but still fit the standard .473 case head/bolt configuration. With that parameter in mind I didn’t want to necessarily design something so unique that I have to invest in manufacturing custom dies, particularly if the performance results turned out to be only so-so.

My design criteria were:
·.473 case head (rim)
·52,000 psi chamber pressure
·Push bullet weights from 125 to 195 grains
·Large enough case to not be pressure sensitive to minor changes in charge weights
·Feed reasonably in a short bolt action rifle
·Caliber length case neck

My solution was to use 284 Win brass that enables the use of a .473 rim but a fatter .500 case head diameter. I fitted that 284 brass into a cut down 8mm Rem Mag full length die to obtain the 8mm neck (.320 length) and 25 degree shoulder. The 284 case head diameter of .500 comes to rest almost half of the length of what would have been the original die before chopping it down.






Pictured are the cut down 8mm Rem Mag Trim die, FL die and seating die. Loaded cartridges are with the 150 grain Hornady bullets at OAL of 2.600. My case necks turned out a bit short due to my learning experience in sizing and fire-forming but more on that later.



Cartridge specs:
·.473 rim, .500 diameter case head
·.488 diameter shoulder
·25 degree shoulder
·.320 neck length
·Max COL 1.891
·58 grains water capacity

More pics and experiences to come on case sizing and forming. I should mention the test rifle chambered for this round is a short action barrel-nut Savage with a Shilen 10 twist 24 inch barrel. More on that too later.

Nels