This is not exactly "short range" or indoor range ammo. It was not used by the STASI for raids. It is not frangible. This ammunition was designed to be used out to 300 meters. The light weight projectile was designed to loose velocity quickly so that once it goes past it's intended useful range it will become less dangerous compared to regular ball ammo that will travel for miles. The plastic core is HARD and does not deform much. As a result it will do considerable damage to whatever it hits. I've fired this ammo through 10" diameter TREES at close range.
It is just as deadly as ball ammo and as such must be treated with as much respect. The official designation was "M-43 Ubung" which literally means "Practice". There are many stories out there about this ammo and what it really is, but it is nothing more than practice ammo for use where the target ranges have limited downrange danger areas. Nothing more. The East Germans made this load from the 1960's through 1990 in vast quantities. It IS corrosive primed and a blast to shoot due to the light recoil. Great in an AK but occasionally jams in an SKS.