Yesterday’s piece about the Russian ADS “amphibious assault rifle” generated a fair amount of curiosity – especially with regards to its special underwater-optimized cartridge…
So, here’s some further info:
This new cartridge is known as 5.45×39 PSP. Externally, it is similar to standard 5.45×39 ammunition except that it has a different bullet shape. Internally it differs in having a long bullet, which has a special shape and protrudes into the cartridge case all the way to the primer flash-holes. The result is an overall bullet length of approximately 53mm (2.1 inch), compared to the complete cartridge length of 57mm.
There are two types of PSP ammunition, the 5.45 PSP (combat ammunition) with a hardened steel projectile weighing 16 grams (muzzle velocity in air about 330 m/s) and 5.45 PSP-U (practice / training ammunition) with bronze projectile weighting 8 grams (muzzle velocity on air about 430 m/s).
Effective range with PSP ammunition varies from 25 meters at 5 meters depth to 18 meters at 20 meters depth; effective range of the PSP-U training ammunition when underwater is about half these distances.