French Army Choose H&K416 to replace FAMAS - The Firearm Blog
Dirt and water don't slow it down.
https://en.wikipedia.org/wiki/Heckler_%26_Koch_HK416
The HK system uses a short-stroke piston driving an operating rod to force the bolt carrier to the rear. This design prevents combustion gases from entering the weapon's interior—a shortcoming with direct impingement systems.[10] The reduction in heat and fouling of the bolt carrier group increases the reliability of the weapon and extends the interval between stoppages. During factory tests the HK416 fired 10,000 rounds in full-auto without malfunctioning.
