This is an experimental ammunition.It’s a product that China is trying to reduce its caliber(12.7x108mm to 10.5x93.5mm).
As a test product, it has not been selected for service by the army and the final model has not yet been determined.
Other case sizes are the same as 12.7x108mm.
Headstamp:41 64(41st Arsenal,1964).
The ammo & .50BMG: