I used a M-4 for 15 months and never jammed once. It was covered in dust (I was a tank commander) and never let me down. The biggest problem we had was the cheap-o mags... they were the cause of double feeds and so many of the problems. Carried a 9mm also and it was a fair lil gun.
It would make gun nuts sick to see all the weapons that are recovered over there and we just blow them up or crush'em with a tank. Dozens of M1's still packed in grease... so many antique guns that could draw serious money over here.