Stupid question time
I was checking into AR-15 ammo, specifically .223, and I noticed that an overwhelmingly high percentage is between 50 and 60 gr. Other rifles have much ammo weighing 4 times that much and even 9mm is over 125 gr. What's the deal with such a light bullet with the ARs?
I don't know much about ammo, so my only guess is that a projectile that light can be thrown much faster, but that is only a guess.