My friend has it, but I don't believe it's legit, he is a sniper about 99% of the time.

I think it is pretty much impossible, doing the challenge with AR and SMG is already hard, try to do it with a 100 bullet mag...

Though, Black Ops had a loop hole for this challenge, it was enough if you fired the entire mag to enemy Cobra, so maybe it could work on MW3 as well, there are several challenges that can be done by doing little cheating.

I got the sniper one. Hardscoping in the bunker at outpost.

u have to do it from long rang and make it on of the weakest lmg with low ammo

Yeah Dictator is definitely impossible.

The smallest mag on LMGs is 100 again right? I have only used the MK46 (iirc) and just being able to hit 75% with an LMG is crazy... much less 100% consecutive bullets.

Yeah I believe the only way to actually get it is by boosting :/ I also tried the chopper thing with all the weapons here but it doesn't seem to work.

Is there a way to get AR/SMG challenges without too much of a hazzle?

mach 7?