My department ended up testing a couple different loads and ended up with Federal Premium 223 62gr SP. Its the LE223T3 version. Our SWAT uses 10.5" barrels and it was best at expansion, glass penetration, and sheet metal.
What's a good round for defensive use in a short barreled AR in 5.56? 10.5 in barrel
Why the emphasis on 5.56 fragmentation velocity, when there are plenty of quality modern expanding bullets available for non-Hague users?
I've used a Mk262 clone on Kentucky deer with a Nosler 77gr CC and it left an exit wound I could easily stick my thumb into...but there was zero evidence of fragmentation on a ~65yd head shot at 2740fps from a 18" SPR that traveled about 10" through neck before exiting, although it was clearly tumbling.
Mk262 is obviously a proven combat load from Mk18s, but I do wonder if an expanding bullet would be a better mousetrap at stub-nose velocities...
The strength of the original design concept of the round is pretty much ignored or even considered an inconvenience. And that's a curious state of affairs.
https://www.indianagunowners.com/forums/ammunition-reloading/405570-do-you-load-tumble.html
I don't know about the original design concepts, but yaw and fragment of 5.56 projectiles isn't dependent on the stability or lack thereof while the bullet is in flight. The projectile starts to rotate and turn sideways in fluids and fluid-like media because the center of mass is biased toward the rear of the bullet. When fired from a barrel with a sufficient twist rate of rifling, the projectile is stabilized while in flight. With the exception of the necessary speed on impact, yawing and fragmenting after impact are independent of the bullet's motion prior to impact.
The idea was to have barely adequate stability. Close in not so much and the velocity promoted break up. Further out, more propensity to tumble and make the holes bigger. Just stuff I learned reading men's magazines in the sixties...
The "tumbling" (actually yawing) is why you saw a permanent wound channel that big. A bullet traveling sideways through flesh makes a big hole, much bigger than an expanding 0.22 inch projectile can. When they fragment after sufficient penetration, the wound channel is huge.
If you find an expanding bullet that suits your needs, go for it!