I think the colonel who was interviewed is not a gun guy, but a procurement guy who likes catch-phrases and emphasizes things that he doesn't really understand. He probably has a sergeant in his command that actually understands this stuff, but is letting him make a fool of himself, for the good of the service.
“The chamber pressure for the standard assault rifle is around 45 KSI [kilopound per square inch], but we’re looking for between 60 and 80 KSI … the chamber pressure when an M1 Abrams tank fires is on that order,” Gordon told Task & Purpose. “We’re looking to reach out around 600 meters and have lethal effects even if the target is protected by body armor.”
If they mean Type IV armour, that is rated to defeat 166 gn M2 AP travelling at 2880 fps
Type III is rated for 7.62mm 148gn FMJ M80 ball at 2750 ft/s
At 600m, that becomes a bloody big ask for anything in the intermediate cartridge range and will require Ludicrous Speed MV's.
So that may be where the talk about needing very high chamber pressures is coming from, but practically we are now talking BFO chamber and barrel thicknesses and barrel life dropping through the floor!