Still having M4 issues

[binicb2r]

I essentially scrapped my old M4 which I was having all shorts of FPS and hopup issues with.

I was given a CA M4 which had the gearbox internals explode. I used the gears, piston and the m120 spring from the old one. I re used the tappet plate and nozzle from the CA since they were in good condition and the nozzle has a better seal. The hopup bucking is brand new and I have tried 3 different hopups, 2 metal and one plastic.

I have great air from the gear box but I chrono around 240FPS and it doesnt not always seem to push the BB far enough into the hopup and the hop up does nothing when the BB does go through.

Any suggestions?

[Deleteplz]

Check the hop up unit's alignment, bucking, etc. It sounds like a classic airseal issue at the hop up unit. Do you still have the hop up unit from the other M4 to test with?

[binicb2r]

Check the hop up unit's alignment, bucking, etc. It sounds like a classic airseal issue at the hop up unit. Do you still have the hop up unit from the other M4 to test with?

It all looks good. The plastic is from the old gun. The metal is a spare and one metal in it. I tore it down and I think I got a seal but I not have trigger issues where the trigger clicks and doent give semi. That only happens with the gear box in the lower. Because of this I cannot test it. I do not want to have to disassemble it again.