Hop up assembled and attached to the inner barrel, removed from the outer barrel.

Start by sliding the inner barrel into the outer barrel.

Keep sliding it in, compressing the spring.

Make sur ethe tabs on the hop up ubnit are aligned with the notches in teh outer barel. They're offset by 90 degrees.

Press the hop up unit all the way in.

Turn the hop up unit 90 degrees.

Release the hop up unit.

The hop up unit will stay in the outer barrel thanks to the tabs.

To remove the hop up unit from the outer barrel, replace the bucking, or to get access to the little tube and hop up actuator, start by removing the retaining clip.

Simply pop it off. Once removed, the inner barrel can be extracted from the hop up unit, if need be. *

Rotate the adjustment wheel so it can slide off over the tabs.

With the wheel removed, you can access the actuator and detent tube.