Promoted Pawn said:
I can think of three special instances where a tactical operator may want the weaker cartridge.
1 The 5.7 may be better if an AP round with less over-penetration is called for.
2 If subsonic munitions are called for the .223 cartridge is just a waste of space..
3 Due to recoil the 5.7 is more accurate than the .223 in full auto.
I think that for these reasons the weapon may have some appeal to those organizations that train with AR style weapons.
1). 5.7 doesn't have enough penetration to begin with. 5.56x45 is the best way to go: good penetration, fragmentation/tumbling, and enough power to punch through soft body armor without the need for "AP" bullets.
3). Standard military doctrine doesn't seem to train soldiers in full auto marksmanship anyhow. You want accuracy? Fire single shots.
The AR-57 is a fun tool but IMHO, it is a step backwards.