On the left is a standard 7.62x54R, in the middle a single case with neck split, and on the right is a 3D model of the complete experimental round, developed in USSR circa 1941. It was tested in a re-barreled Tokarev carbine, and found to be too powerful for it. MV was in excess of 1000 m/s.
Very little info is available on it, and it is possible that the case shown is the only one surviving example.
only surviving example and accidentally fired in a 7.62 chamber?
That doesn’t look like a normal “fired in larger diameter bore” type of situation. Typically the neck would bulge out and split, not petal like that?
local experts think that split is due to internal stress over improper heat treat
A normal tokarev has groves in the chamber to help with the extraction of the case. These splits look to constant to be caused by only stress.
Brings to mind the 6x49mm Unified
I want to revive this thread and bring to question an item that came up in the recent auction (link at bottom of post). It’s a 12.7x99 casing, primerless, and possibly a wildcat or something (doesn’t look quite right to be a 12.7 casing) but with split neck in the same fashion as this 5.6x60.
Does anyone know anything about this 12.7 casing and how it came to be split in this manner?
Looks like the neck was not annealed after production or?