You should check out the reviews on
http://www.airsoftretreat.com/reviews/ for agm and utg; they have break-downs of the rifles and possibly upgrades. The WELL Warrior 1 L96 underground suggested is another good consideration.
It seems your set on L96 but, even though it's not a L96; JG BAR-10 is a consideration cause of the good quality and upgradability (this also reviewed on airsoft retreat) using TM VSR-10 parts