It's not a great choice for home defense, however - it's actually quite bad at killing people. A nutjob with a couple of 5.56mm holes can still stab you a bunch of times before he bleeds out.

A shotgun is a far better choice.

Fun fact: the reason the military went with 5.56mm is that killing power is less important for the military (wounding a guy takes him out of the fight, as well as 1-2 of his buddies to take him home), while ammunition weight is a big deal (lighter ammo = less for a soldier to carry).

Just to bring this to something technical and marginally less depressing than discussing mass murders on HN on Christmas, 5.56mm got a lot better with the 75gr TAP and 77gr Sierra OTM/mk 262 vs. M193 or M855 ball. My HD long guns are a tricked-out Mossberg 590A1 and an M1A 16" .308 carbine with 180gr ammo, though.

I mean, the military even manages to make 9mm ineffective. LC 115gr 9mm FMJ is maybe 10% as effective as my Speer Gold Dot 124gr +P JHP.

I think a lot of the differences in lethality can be attributed to the military's inability to use anything other than ball or jacketed ammunition.

SWAT entry teams use them. At close range they're quite a bit more effective than at the longer ranges often encountered in military situations, since the bullet is likely to fragment.

At the same time, tests have shown less overpenetration after encountering drywall than hollowpoint handgun rounds, which tend to fill up the hollowpoint without expanding and then go through several barriers.

Do SWAT teams use full metal jacket rounds? Perhaps that might partially explain a difference in lethality between military use and SWAT use.