So first of all you need one maxed lvl Assault Rifle (no matter which). Get Gunbutt kills

1. Double Time
   
2. Overkill or Restock
   
3. Tracker

Take Stun and any grenade, but not lethal knife. Because if you kill with hit gunbutt not works instead of that you use your knife.

Now I'll show it with M4A1
Muzzle: Breacher Device To get 1 hit kill.
Barrel : FSS 11.5 Commando To run or slide faster
Stock : No stock Increases your speed
Underbarrel : M203 40mm Conclussive To immediatly stun when you see enemy or additional stun grenade. By the way you can remove it to move way more faster and use other random thing instead of this.
Perk : Fast Melee Like if you miss first hit you have chance to do it again in short time.




And for secondary I recommend to take shield to recover your ass. Or just take restock