1) The M-16 rifle: Thumbs down. Chronic jamming problems with the talcum powder like sand over there. The sand is everywhere. Jordan says you feel filthy 2 minutes after coming out of the shower. The M-4 carbine version is more popular because its lighter and shorter, but it has jamming problems also. They like the ability to mount the various optical gunsights and weapons lights on the picattiny rails, but the weapon itself is not great in a desert environment. They all hate the 5.56mm (.223) round. Poor penetration on the cinderblock structure common over there and even torso hits can't be reliably counted on to put the enemy down. Fun fact: Random autopsies on dead insurgents shows a high level of opiate use.
2) The M243 SAW (squad assault weapon): .223 cal. Drum fed light machine gun. Big thumbs down. Universally considered a piece of shit. Chronic jamming problems, most of which require partial disassembly. (that's fun in the middle of a firefight).High level of opiate use means they are stoned on downers and feel no pain, so the .223 and 9mm ammo will kill them but won't put them DOWN and make them stop shooting before they finally bleed out. Hardball ammo doesn't fragment, doesn't do enough instant damage to stop a guy who's stoned. Guess what the Canadian Forces is armed with: M-16, M-243 SAW and Browning 9mm. Wonderful!
3) The M9 Beretta 9mm: Mixed bag. Good gun, performs well in desert environment; but they all hate the 9mm cartridge. The use of handguns for self-defense is actually fairly common. Same old story on the 9mm: Bad guys hit multiple times and still in the fight.
On the other hand:
8) The M-14: Thumbs up. They are being re-issued in bulk, mostly in a modified version to special ops guys. Modifications include lightweight Kevlar stocks and low power red dot or ACOG sights. Very reliable in the sandy environment, and they love the 7.62 round.Shoot a guy with 7.62 NATO and he's going down, stoned or not. Also good on cars, walls, trees, etc. The Brits have made the same discovery I hear, and are re-issuing the 7.62mm FN-FAL instead of the jammy, puny Enfield bullpup .223 poodle gun.
Look for new development of proper battle rifles in the near future. Probably look simple like the Kalashnikov but with a decent muzzle brake, plastic furniture and .308 ammo. Real men need a real gun.