Yes, the U.S. Army did plenty of testing. Unfortunately, only FMJ can be used in either 9mm or .45 ACP. FMJ also isn't normally what one would pick if one could have something better.
I'm not sure what 230gr advocates think the advantage of weight is in such a round, but anytime you can get a hollowpoint to open up, it's going to increase the stopping power. With a 230gr FMJ, you're not going to get much expansion unless you hit a hip or skull. With lighter bullets, you'll get more velocity, a good chance for expansion, a better temporary wound channel and less recoil. Add a little more velocity to it (in the form of +P), and it's even better.
I have a friend who not only fought in Korea, he wrote a book on the fighting ability of various foreign troops there. In the cold northern areas where the Chinese troops wore heavy clothing, there were many cases where they'd find bodies, pierced with machine gun ammo, but with multiple .45 ACP ammo lodged in the quilt-like coats. It was the machine gun fire that killed them, but it's the .45 bullets that didn't make it through that interested the military.
I've talked to, and read about, a number of soldiers who didn't feel that the .45 ACP ammo lived up to its larger-than-life reputation. And though I don't go so far as to worthless (which a lot of these guys unfortunately concluded), I will say there's a lot of BS that accompanies the .45 ACP folklore.
My friend (above) also told me that the Colt 1911s jammed repeatedly in cold weather. This was no fault of the gun or the ammo—just the fact that it was bitter cold and lubrication, being what it ain't, just wasn't doing the job.
Until recently, I thought all the military guys would have preferred .45 Colt autos, but a friend of mine who just got back from a third tour to Iraq, said that with a choice of firepower over stopping power, that it would be firepower every time. If they used their 9mm Berettas, they wanted full magazines and the ability to throw a lot of lead at the enemy.
So not everything's as clear cut as one might think. And as far as the military trials went, just remember that they were comparing FMJs against FMJs. Had they changed the 9mm to JHPs, the results could have been far, far different.
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