Fellas: It doesn't matter a schmidt if the cartridge you're using is supposed to be the end all to be all, or if some feel it is better to wound an opponent so that it takes two of his buddies to cart him away. If the dang thing doesn't just knock them down and out of the fight with the first hit it is going to be a useless exercise in self defense when there are so many of them that they compleetely overwhelm you, whether they are shot up or otherwise.
If you have a 30 round magazine and a 3 round burst devise and find that you need three rounds to drop a charging opponent, you are gonna be schmidt outta luck before you know it.
It is fine to talk ballistic theory about what round is best in combat and it is a warming thought to the grunt behind the rifle to know that one hit from a such and such caliber all the way out to the end of the ball field will penetrate this and that, but if they are comin' head on for all they're worth and your hits don't take 'em down, things get real critical real fast.
It was often said that if the 401 Winchester had been chambered in the M1 Carbine, there would never have been a 30 caliber carbine round. I can agree with that. A fat slug at medium velocities usually pounds them right down and keeps them there. So do the faster moving 30 calibers.
We used to know when Charlie was gonna hit us. You could smell his hasish and hear them getting all psyched up for the attack. When they would come at us, we found the M16 didn't knock em down and keep them there. Sometimes we would have to unload too many rounds to either hit them or keep them down. What worked was the M14 and the M3 greasegun (at closer ranges). What works is a heavy, slow or medium speed bullet. Maybe if we take the 223 and straight case the dang thing, load it up with something in the range 160-220 grains, it would work better as a close range weapon with some different loads for longer ranges.
Yes, the new SS-109 rounds will penetrate a helmet at 800 meters, if you can hit it. You might be able to even see a slow fat slug moving out that far but you would know that if it hit an opponent, they would go down, regardless of the range. You know, the AK is considered a medium range assault weapon. Although they have ladder sights for up to 2 klics, the darn things can't hit beyond 300 meters, with any effectiveness. Now, straight case that round and you are real close to the old 401 Winchester. At the same ranges that would make an excellent battle round.
If it's a matter of battle gear weight for the GI, then instead of carrying more of the lesser effective rounds, toughen up and carry the same number of heavier rounds. It sure seems to me that no matter what weight bullets you carry, when the schmidt hits the fan and you have to rapid fire at multiple approaching targets that don't take 'no' for an answer, the only answer is to puyt them down hard, and regardless of bullet weight, you are gonna keep firing until they hit the ground - preferably dead. Just my two cents worth. Mikey.