Semi or full automatic Marauder?

[Doc]

Guys, I have been pondering building an automatic Marauder. It would require a new Breech, shroud and baffles. I want to make a gas piston ride around the barrel inside a larger diameter shroud. The shroud and piston have to be large enough in diameter to create enough force to cock the hammer as well as over come the piston and bolt return spring. It would operate similar to the FX gun using only wasted air trapped by baffles and shroud. I have a device that can trap all most all of this air. As the piston moves fully rearward instead of venting the air to atmosphere the remaining air if any could be vented to the other side of the piston to aid with bolt closure. By using lip seals on the piston the return air could bleed off or it may require a very small bleed hole. My thoughts are none of this begins to move until the pellet has exited the barrel so no velocity or accuracy is lost. Wouldnt increase air consumption and may make the gun quieter as its doing work with wasted air. Depends on if there is enough wasted air pressure and sufficient surface area of the piston to operate but there is on the FX so why not the Marauder. I dont really want to port the barrel and use a gas block like an AR or SKS.

[Motorhead]

Doable with the correct mechanics present.
Downside being more efficient a tune you do, Worse becomes the excess air volume you seek in driving your auto cocking mechanics

You do this .. Post it up


Came back to add ...
Keep in mind the WHY gas guns vent off barrel BEFORE projectile exits muzzle. This so the pressure pulse following bullet/pellet takes the route of least resistance first driving the cocking mechanics.
* Once bullet/pellet leaves muzzle the area & clearance required to exit projectile dissipates this pressure energy VERY QUICKLY !!
As above ... pressure seeks the route of least resistance being that path bullet took

[Doc]

I understand why powder burners take the gas from a port in the barrel but they function a bit different as in the brass cartridge grips the chamber walls during firing and peak pressure the AR15 also has a rotating locking bolt. I cant see any way to do an inertia type system like a .22 rim fire with the magazines we need for diabolo pellets. My main concern is getting it right without it being overly finicky to tunes and fill pressures. My thinking is a piston system which has a bit of overkill operating after the pellet leaves the barrel. The FX gun operates on pressure captured in a small LCD and transfered to a piston through a tube. Interested in hearing from all you other gear heads on here and thought it would be a fun project.

[Doc]

www.youtube.com/watch?v=CcVeslwTvAw



Check out this old video explanation of semi and full auto triggers.

[BDSKJChris]

my first thought would be to use air after the air stripper, there is more than enough excess air after the pellet leaves the muzzle to run the bolt.

the system (gas impingement or gas piston) would have to be extremely efficient and timed to allow the pellet to exit the muzzle before the bolt is withdrawn from the breach or the barrel would de-pressurize and the pellet will have little to no velocity.

another thought would be to have the cycling mechanism be separate from the air driving the pellet.

the second option would be driven by something like a 12 gram co2 cartridge or could use a nitrogen charged piston that has almost enough power to cock the bolt and would only use a small amount of air pressure and volume to generate enough force to drive the bolt all the way back and then it would return to battery under the nitro cylinder power.

as always there are many ways to skin a cat, I lack the spare time to do much so my solution would be to buy an fx monsoon or revolution.

[Doc]

I agree that taking air after pellet exits barrel would be best and thats how the FX guns do it. It will still require a gas piston to have enough force to overcome the hammer spring and bolt return spring. It would be way to finicky to operate with a ported barrel and timed system. I wanted the gas piston to be near the breach but I am sure the volume in the shroud would drop the pressure below whats needed. If the piston is right behind the muzzle the rest of the shroud becomes dead space unless I can vent the air to the other side of the piston after the bolt is fully open. Then there is the semi auto trigger to build. Oh well it would still be a fun project and I have the time, tools and ability to do it.