I find that its mostly people who dont know what they are talking about are the ones that say "the M4 is a peice of _____ fill in the blank." I never had problems with my peice, even in the sand. Gets dirty? Clean it. Broken? Fix it.
M249? Great weapon as well. Clean it.
M9? Clean it and it will work. Take care of those mags too.
M2 .50 cal? If we could find an armoror who knew how to fix them, Id bite. Im a 240 man myself.
M14? Priceless.
Always, especially as a machine gunner, keep that gun rag in your cargo pocket with a little bottle of CLP and all will be well.
I will add though, that reports of substandard terminal "performance" of 5.56 M855 are somewhat true. Shot placement is key, but even well placed 5.56 rounds dont always produce immediate results.
Nothing hits like an M80 ball or M118LR though... but even then...
Guess thats why its called "ballistics".
Nothing pisses me off more than a dirty weapon........