I get that AP bullet, but what is this talk about bullet weights? Some misunderstanding or is it really going to be limited in US?
Heavier bullets do have more penetration capability, but .223 was designed as fast to have flat trajectory and to cause much tissue damage. Banning heavier bullets might lessen penetration but lighter bullets cause more damage to tissue (unarmoured targets). .223 bullets weighting less than 40 grains are quite "explosive". Not that those lighter bullets should be banned, but I don't see the point in limiting those as the only bullets to be available for that caliber.
Example:
"V-MAX™ Bullets
Hornady’s V-MAX bullets consistently achieve rapid fragmentation at all practical varmint shooting velocities."
Hornady Manufacturing Company :: Ammunition :: Rifle :: Choose by Caliber :: 223 Rem :: 223 Rem 40 gr V-MAX®