Two forms of ammunition were used by the Soviets in all of their 50mm mortars.  These were the O-822 and the O-822Sh.  The shells are virtually identical and can even share fuses.  The easiest method for telling the difference between the two is by the number of tail fins.  The O-822 has six fins while the O-822Sh has only four.

Regardless of type the 50mm shells are impact detonated high explosive weapons with blast effects similar to a hand grenade.  The small propellant charge and primer are located in the base of the round, where they are activated by being dropped down the mortar and impacting a striker at the bottom of the tube.  This activates the primer, which ignites the propellant, and launches the round..

The rounds were shipped in wooden crates with a safety cap installed in place of a fuse.  When they were in the field they were transported in metal transit cases of seven rounds.  When in these cases the safety cap would have been replaced by either the M-50 or MP fuses.