The KE weapon in the XM29 is based on the HK G36, probably the most advanced assault rifle in service.
Plus, the XM29 has a fire control system which gives it ridiculous effectiveness on the battlefield. You point at what you want to hit, and it figures out where you need to aim. You aim at the spot it tells you, then pull the trigger, and it will compensate for your movement of the gun and fire the round at the instant you are nearest to the correct aimpoint, and it compensates for recoil. It pretty much turns every soldier into Vasiliy Zaitsev.
And of course, the HE part of the weapon, the real meat of the program, is even nastier.