Found it online earlier today from somebody else, not everyone has gotten past the MOUT training or gotten to play online.
If you're wondering what the other weapons are like, instead of just the M16, M16/M203, SAW, and grenades are like from the single player training missions then I've got some codes for you to try on the firing range.
Bring down the console with the tilda ~ key and then type without quotes, "mpcheat changeclass x"
Where "x" equals one of these combination of letters.
s= the Barett M82
svd= dragnov
ak= AK47, or possibly AK74 cause it has so little recoil
m= M4 carbine
Plus you get a stock of grenades as well, it's kinda fun to monkey around on the firing range with the stuff.
I'll post more weapon/class types as I figure them out. The recoil of the M82 is hillarious.