Have a A-15 chambered for .223/5.56, bought .222 ammo by mistake. Will it work?
No. Being the length of a 222 case is .060 shorter than the 223 the bullet will have too far of a jump to reach the lands. You could be facing catastrophic failure trying it. Typically bullets are only .020 off the lands.
I doubt it.
No it won't. Don't try it. I've got a .222 where do ya live?
Nope, will cause a major problem