Hear me out… is technically possible.

[Dauntless152]

Think of an AR15 hammer, or a revolver, and think about a properly tuned valve. I am sure if a couple of us put our heads together we could come up with something super small and still super reliable as a pump gun. Thoughts ?

[Grendel]

Theoretically it should work, a hammer is a hammer. You would have to do some experimentation to get the mass of the hammer, the spring strength to work with the valve and have appropriate dwell but can not see a reason it wouldn't work. How do you see adjusting velocity? Adjusting a clock spring is possible but not as flexible as adjusting preload on a compression spring.

[Siress]

I started designing something with a similar intent, actually. A mechanical sear actuated unbalanced spool valve. Imagine this with a sear holding the firing spool instead of air pressure - but engineered to have a lower force applied on the since it'll be sear actuated, and pump return to reset the firing mechanism.

[Redragoon]

I believe this was used in the Proto SLG design. Single Spool piece held back by a mechanical sear. Clapper solenoid moves sear lever which would release the bolt.

Drawback was the lower rate of fire compared to an air sear and some reliability issues at higher rates of fire. Sear not always catching, etc. At 10.5 bps it worked well in the one gun I used. Never really got much time with it, though.

[The Inflicted]

My SLG was exceedingly fast. https://youtu.be/K_Pjsmx3ijc After working with it for a couple years I think most of the problems could be chalked up to DYE/Proto's decision to use a standard 9volt to power the gun rather than a dedicated power pack as on an E-Mag. The lack of available amperage meant that the sear spring was just barely strong enough to retain the spool. If you so much as over-lubricated the gun it could go into runaway full auto. Conversely, if you stretched the spring even a bit you would have a situation where it would take multiple trigger pulls to fire the gun.

[Siress]

Thanks for pointing out the SLG! Not sure why they did that for a semi-auto. Kind of odd. Sounds like their undoing was adding electronics into the mix.

[Lt. head-shot]

This is essentially how the Dukie DRV worked. Instead of hitting the front of a nelson powertube, it hit it from the back, which pushed the power tube forward and then released gas through the tube. Most of the complexity on the rest of that gun was from the rotation mechanism and how it interacted with the trigger/hammer setup.

[Dauntless152]

That’s pretty awesome. I would love to see this in a extremely tight set up, and just see how tiny we could make something like this

[Lane]

You could hinge the hammer in the frame and have it connected to an extension or compression spring rather than a coil. Then adjusting the length of compression/extension will have an effect on the velocity. Look at how some revolvers position the hammer spring.

[flyweightnate]

What about the lever valves in ICD cats? Have the hammer travel vertically in the frame, and hit the back of a horizontal valve.

[Spider!]

I like the idea of a rotating hammer, with a compression spring in a printed frame.

The thing I've never been able to get to is, "what advantage does it provide to the layout?". The hammer could have a longer travel, so trade some mass for kinetic energy. That's the only thing I've come up with that is unique.

[XEMON]

What you are describing has "nearly" been done ... The thumper had a rotary hammer, but with a linear hammer.
One of the main issue is that the hammer force the valve pin sideways which cause it to bend and deform over time ...

That being said, I love the idea of a coil spring in the handle to make the marker even more compact 👍