2 different assignments, maybe 3.

Name: Primary Weapons Master
Goal: Get 500 kills with each Primary weapons; Assault, Engineer, Support, Recon, Shotgun, and PDW
The M26 Mass would have to could as a shotgun even though it's a gadget.

Name: Pistol Master
Goal: Get 500 kills with each Pistols

Possible 3rd idea.
Name: Gadget Master
Goal: Get 500 kills with each; RPG, SMAW, M320, Stinger, IGLA, Javelin, Xbow and Xbow Scoped.
Optionally add: C4, Claymore, AT Mines, Mortar.
Before someone asks, 'why not the repair tool, eod bot or mav, maybe even the defib?' while they can be used as weapons that is not they their purpose is.

Instead of listing each weapon maybe it can just calculate it base on percentage.
If I counted them correctly there are 60 Primary weapons and using me as an example, I have 22 weapons at 500+, show it should show up as having 2.72% completed.