I have been told that the 5.7 round is a specialty round and that is the reason for the price of ammo. I'm not sure I understand that (speacialty round). I mean is it because it's a new round in the US or is because it's a marketing gimic to raise the price of the round?I was talking with my cousin and he was saying that the 5.7 round was cheaper than the 5.6 or 223 round.I do admit I do not have many rounds for my ps90 but I hope to change that after I pay my rifle off.