SACair Forum

I've been working on my friends broken M4. The problem is it shoots with little to no velocity. The bb shoots about 15 feet and falls. I opened the gearbox up and could find nothing that would cause this. Piston and head were fine, no gaps or loss of air, any ideas? I would like to try to fix it before the game today so any help would be greatly appreciated.

Cylinder head, air nozzle, gap between hop up unit and gearbox, bucking, or maybe a bent body/outer barrel.