I don’t know what Tx or Waco uses but here is a MA study that recommends the .223 FMJ.
In the study they point out that even the FMJ starts to tumble at about 4.5 inches penetration and then will most likely fragment.
Only the bonded tactical bullet tends to hold together.
http://www.mlefiaa.org/files/ERPR/Ammunition_20for_20the_20Patrol_20Carbine.pdf
That article is at least ten years old as the latest reference is 2003. Not that there have been any new revelations in the interval but read the results section. The author almosts quotes what I posted verbatim. The objective was to take into account the need to penetrate windshields, body armor, etc. again, not relevant at Waco.