I would if it may someday be used for serious purposes, but I seldom do anymore with my plinking or target ammo, and have never had any issues. I guess it would depend somewhat on how smoothly your rifle/magazines tend to feed. I think if it tends to shove the bullet nose against the barrel extension/locking lugs upon feeding, you may want to put a bit of crimp on them.
You certainly don't need to worry about the bullet getting set back in a round in the magazine with .223 recoil. which is the reason to crimp that is most often given when loading heavy hunting ammo in dangerous-game cartridges, where it can and does happen.
edited to add: all those words after the comma in the last sentence!
Edited by RONK - August/30/2009 at 18:01