I had missed this in June from Bob Owens:

I’m also perplexed that FN submitted the Five-SeveN, as the gun’s 5.7×28 caliber has been thoroughly trashed by most defensive handgun experts as a niche round that fails to create adequate tissue damage to have significant immediate impact on targets.

The FN 5.7 won’t be the next Army handgun, but it doesn’t perplex me at all, and frankly I wouldn’t pay much attention to defensive handgun “experts” as they trash things.  And this is as good a chance as any to post a related bit of analysis I ran up on a few months ago.

The FN 5.7 pistol is constantly maligned or underestimated in many gun forums and articles, often by people who have never experienced shooting the pistol. Subjective comparisons with the .22 magnum or categorization as a sub-par .223 round create confusion about the effectiveness of the FN 5.7.

Enough time has passed after the terrorist attack at Ft. Hood. The shooter, Nidal Malik Hassan, has been arrested, tried and sentenced. The media has moved on. Now we can begin to analyze the impact of the FN 5.7 and address the question of lethality.

Using SS192 and SS197SR ammunition (common commercial 5.7×28 ammo), several 20-30 round magazines and an FN 5.7 (shooter also had a .357 revolver but did not use it), Hassan killed 13 and wounded 32 people.

Many armchair ballistics expert criticized this result as proof that the FN 5.7 platform is not lethal enough because of the proportion of the fatalities to the wounded. Others have proposed that had Hassan use another type of pistol, 9mm or .45, there would have been more fatalities.

If you look at this Wikipedia link and look at the list of casualties, one can come to a very eye-opening conclusion.
Fort Hood shooting – Wikipedia, the free encyclopedia

1. 11 people were shot center-of-mass (COM), one was shot in the stomach and one was shot in the head. All 13 died. All 11 victims who were shot COM did not survive.
2. 3 of the 13 people who died, tried to charge Hassan, but he stopped them with COM shots.
3. The 32 people who were wounded were hit in the arms, legs, hips and shoulders. None of the wounded survivors were shot COM.

The following conclusions can be drawn:
1. The FN 5.7 is a very lethal round CQB because all 11 victims who were shot COM died. No survivors for those hit COM.
2. The FN 5.7 is a real stopper, because 3 tried to charge Hassan at close range and were stopped by COM shots.
3. One of the fatalities was shot in the stomach, and died. The fragmentation of the SS197R round can create a hail of metal shards that can cause serious internal organ damage and bleeding in the stomach.
4. None of the 32 people who were hit in the extremities, hips and shoulders were able to muster a counter-attack because the FN 5.7 must have shattered or broken bones. The high rate of wounded vicitms to fatalities was the direct result of the shooting ability of Hassan (or lack thereof), and not because the 5.7×28 round is not lethal.
5. Sgt. Kimberly Munley (base civilian police), one of the first responders, was immediately disabled with 5.7×28 bullet shrapnels to her wrist and a second 5.7×28 bullet broke her femur. The light 5.7×28 commercial ammo showed that it can shatter large bones due to its velocity
6. According to medical personnel, there was so much blood in the room that it was difficult to get to the victims because the floor became very slippery. One can conclude that the commercial 5.7×28 rounds can fragment or tumble, causing immense blood loss.
7. It took five bullets (which I assume was a 9 mm) from Sgt Mark Todd to stop Hasan. And he survived his wounds (no available info on where he was hit, except that one of the bullets paralyzed Hasan).

In conclusion:
1. The FN 5.7 is definitely a very lethal round. 100% fatality for COM shots.
2. The FN 5.7 is a man-stopper. Three military men tried to charge Hasan, and all three were stopped.
2. The FN 5.7 is a very incapacitating round, if extremities are hit, because it is powerful enough to break the femur (which is the largest bone in the body)
3. The fragmentation or tumbling effect of commercial ammo can cause a lot of blood loss.

The FN 5.7 is a very effective weapon. It is as effective as, or arguably more effective, than any military or civilian pistols in the market.

It is unfortunate that the jihadist Hassan used this weapon against U.S. soldiers.

And as it pertains to its penetrating capability, you can see these tests for yourself (note that none of these rounds are the steel core rounds, and perhaps for maximum tissue damage one wouldn’t want to use steel core rounds anyway).