When I got home I got on the internet and found out that it is for only one firearm, the HK MP7 a PDW that is semi-auto/full auto and cannot be owned by a private person. Restricted to law enforcement only. The round is designed to penetrate body armor, it has a steel core. Only thing I can think of for why it was for sale at the LGS was possibly one of the local PD's had requested the store stock some for individual LEO to purchase for practice. I was surprised at the price, $39.99 for 50 rounds. Learned something new today.