Personal Firearms Proficiency (D20 Modern Feat)
From D&D Wiki
This Feat is what you need to unlock single handed weapons such as the M7/Caseless Submachine Gun, the Brute Plasma rifle, and the Mauler. All of these weapons that require the personal firearms proficiency may be able to dual wield if you get the Weapon Focus feat. You may also get the Weapon specialization feat after you have unlocked the Longarms proficiency feat, the personal firearms proficiency feat,the Exotic Firearms Proficiency, and the Tools level 1 feats.