This is a pretty difficult achievement made to look easy by user PowerPyx in this video:
He/She uses the Gorgon with a reflex scope, grip, FMJ, extended mag, rapid fire and fast mags. He/She also uses the War Machine for their secondary. For the lethal grenade slot they chose a trip mine and placed 2 EMP's in the tactical slot. For the TAC-RIG they placed repulsor armor and traversal enhancement. Last but not least, primary gunfighter 1-3 in the wildcard slots. Good luck you guys!