The Q-System has the highest base damage of all three Atlas assault rifles and the lowest base fire rate. The Q-System's barrel will always grant it the "Cost-Effective" prefix, meaning it fires two bullets at the cost of one ammo, effectively doubling its damage output. With no major penalties to its other stats, Q-System vastly outperforms other Atlas assault rifles and is one of the few common weapons able to compete with legendaries on higher difficulties.
The Q-System is obtained randomly from any suitable loot source.
The O.P.Q. System is a legendary version of the Q-System. Instead of shooting a tracker, the O.P.Q. System launches smaller versions of itself that track and shoot whatever you shoot.