Adding a Adjustable Hopup to the Wingun 731

[Kingsix]

Couldn't sleep a few nights ago because of a caffeine high.

I decided to see if I could improve the preformance of my Gunheaven M36 Revolver/Wingun 731 Series. Although I have the 2" Barrel I would believe the 2.5" Barrel Barrel Model would be the same. The Revolver like many wingun models do not come with a built in hopup unit.

The Newer WG/ASG 715's with a adjustable hopup or Fixed Hopup revolvers, TM, Tanaka, KWC Colt python etc are built with hopup units. Therefore most Wingun revolvers have dismal range unless run at high velocities.

This is a very simple hopup very similar to the ones on A&K Springer shotguns and AGM Sten. It is not a fancy RHOP/Flathop but a standard hopup to hopefully give my Detective special abit more range.





Wingun's 731 series model Revolvers already include a grub screw on the very top of the barrel out of the box. This Hole is not drilled all the way through to the inner barrel. The Grub screw along with a small roll pin keep the Barrel attached to the frame.

You do want to remove the inner barrel before drilling through the outer barrel to avoid damage to the inner Barrel.



The inner Barrel is shortened so it no longer makes contact with the spring loaded Chamber. A pipe cutter was used to slowly cut the barrel shorter with a fine file to clean up.


The revolver is then resembled without the grub screw. A hopup window location is marked lightly with a small drill bit. The Gun is then taken apart and a hole was drilled on the outer barrel to form the hopup window. A file to form the square shaped hopup window.

To Assemble the hopup unit. A standard AEG Bucking and Rubber was used. A Precision screw driver was used to center the nub and Barrel. The Grub screw was tightened to push down on the rubber nub. This in terms holds the inner barrel in place from rotating. The Inner Barrel does not make contact with the firing chamber and thus does not shift around.


I did initially try just using the grub screw as the nub but I found it would split bbs in half. After Installing the AEG Nub the Revolver was able to shoot the BB in a more flat trajectory. However with the 2" Barrel I was not able to hit anything accurately. (I'm a bad shot with pistols ).

I have tested the revolver with .25s and .28's without failure yet. Maybe a 3D printed hopup chamber would be a nice addition because of the space inside the outer Barrel.

Because of the Nature of Airsoft Revolvers Single action and Double action firing create different velocity setting the hopup is dependent on the user style.

If the hopup is set to single action then firing in double action will cause the bbs to fall short of intended point of aim.

If the hopup is set to double action then the shooter may have to aim lower to correct for excessive bb climb.