If autoglass is a concern then you want to go with as heavy a barrier blind load as you can get since you want as much bullet as possible making it through. If its just HD and less concern for autoglass then 55gr TBBC is just fine.
Is that the .223 version of the vaunted “FBI round”? The ones I have are basically a “Trophy Bonded Bear Claw” loaded to 5.56 pressure. The nomenclature is XM556SBCT3
Disregard, I saw you were referencing the 55gr flavor. Sorry.
For HD use and ranges any reputable soft point/hollow point/bonded bullet will be devastating on an assailant. The only type of round I would stay away from are the fast expanding varmint type bullets that would have questionable performance through any type of barrier.
This… I think people get too wrapped up on ammo for the rifles. Our duty ammo doesnt do great in the FBI testing. Yet time and again Ive seen it perform well through windshields, auto body, and penetrating limbs before hitting the torso. Our duty ammo is Federal TRU 223E which uses a 55 grain Gameking hollow point bullet. The front tends to expand and fragment pretty well while the base punches deeper.
Barnes 62gr TSX bullet - VOR-TX would be my choice among those listed. I use it with regular carbine length barrels for deer at reasonable range. It should do fine from an SBR due to its high velocity, almost 2,700 fps frim a 10.3" barrel, excellent expansion, deep penetration (easily barrier blind), 100% weight retention.
Kyle was forced to use M193 in his M4. Its what they had, what Hague Convention allowed, but its a poor choice in comparison to today’s far superior terminal ballistics for civilian/hunting/LE use.
And, most of Kyle’s kills were with his .300 Win., not 5.56.