My M4 hasn't jammed. As long as the inside stays clean and dry, no problems so far. We that are infantry take care of our weapons a lot better than other MOS's.
Some of the Iraqi's are using M16's now. We pulled out of Baghdad a few days ago and saw a pickup truck stuffed with IA's (Iraqi Army) and they all had M16's.
It's not really sandy where I'm at, it's more like clay. You find a lot of sand further south down around Bucca and the Kuwait border. After every convoy we have to wipe down the dust, but that's about it. It does get very dusty, just like Ft. Hood or any other post where you're moving a lot of vehicles on gravel roads. Not much differant.
We got ambushed a week ago on our way back from Bucca (heading north) by about 12 guys with AK's and an RPG. Our M2's quickly took care of that. The idiots set up their ambush on the inside of the curve, and we had 4 gun trucks with 50's instantly fire back. It was over in a matter of seconds. We didn't stop, just kept on rolling. Nobody hurt on our side.