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[HP_Lovecraft]

I could find the link to last years thread, so this is part 2-
Last year I converted one of my Z's to pump, but had some problems, so I put off the project.

From last year:


First problem was the FPS was extremely eratic. Running a pump on liquid simply does not work since you are not firing enough to keep the valve saturated with liquid. The result is the FPS jumps up and down from 270 to 350! The high FPS was because the hammer is no longer connected to the bolt, so the reduced friction increases its energy.

I figured I'd have to convert the valve over to gas, or track down a gas-valve. Both solutions seemed unlikely, but then the obvious occured to me. The reduced friction likely means that I can run just gas, with the valve unmodified to get my target FPS. So I bought a non-siphon, and it actually worked perfectly!

Next problem was the backbottle. I don't like back-bottle tanks, but I dislike bottomline tanks even more. I wanted a niec vert mount, to which I can run a small 3.5oz tank. Fortunetly, this solution was easy. I picked up a automag vert ASA, and rigged it up to fit. Eventually I want to hardline directly to the valve, but for now, I have it running a stainless braided line to the backbottle.

Next problem was the bolt rod. Too much friction, and never figured out why. Turned out it was just some incorrect bends, causing it to bind up inside the gun. After that was fixed, the pump is SMOOTH. So smooth that it moves by it self. Doh! Now it needs a pump spring, and because of the bends I made, I'm not sure I can fit one. However, I think a good solution might be to put the spring on the ROD itself, and not around the barrel.

Otherwise, it seems to run perfect now.
I like stocks, but they are all being used on other guns. So I picked up a real Tommy gun stock. Have not figured out how to attach it, but my plan is to just drill/tap a nice beefy 1/4" hole into the rear receiver, then carve the stock around the shape of the body, and bolt the sucker directly in:

So far:

[HurtCow]

Dude, that's uber-ghetto! I love it.

[HP_Lovecraft]

Originally Posted by HurtCow

Dude, that's uber-ghetto! I love it.

LOL. no kidding.

It started out as a "proof of concept", to test the rod-through-feedblock idea.

Now that the quirks are worked out, the next step is cosmetics. IE match annodizing all the parts, a nice wood pump (maybe tommy foregrip?). Should look pretty when done.

nick

[Schmitti]

Could you put a sleever on the front side of the rod with a washer between the sleeve and spring so you don't bind the spring at the bend where it gets close to the barrel.... otherwise, spring over the pump rod seems very do-able.

You'll have to bring this with you to castle, just for giggles and boasting rights.

E