The joys of being a bachelor with a 3 day weekend! I haven't played much more than you in total though. 82 hours to your 71.

And it's not the M416, the M16. The burst fire one. 
After that it's the Scar H, AUG, L85A2, and AR160.

The thing is, I mostly play Obliteration. That's where all my kills come from.