Good morning, I'm working on a semi auto Mk1 right now and i'm having cycling issues. the gun will not cycle back after it fires.
- the gun is a mk1 upper receiver mounted on a mk2 lower
- I'm using MK 7 military ammo to test the gun
- I've tried adjusting the gas regulator to all 4 positions - no change
- 1 thing have noticed is that the piston, when fully forward, is only halfway the front gas vents on the gas cylinder.

Any idea what could cause the issue? thanks
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