As above. I've only completed 3 missions and already my fully upgraded gun is not powerful enough to complete the 4th. The T5 minigun will only power up to 1587 and yet the mission requires 1589. As the enemies ALWAYS win when your weapon is just a couple of points under the survival missions are impossible to finish. This is a ridiculous situation. If you were able to upgrade the gun to 1590 you'd sail through easily!