Spump build from circa 2008

[RattManDu]

I used to have a build thread on this Spyder pump a decade ago, but seeing as how that's lost and I take better photographs now, I figured I'd throw it back up here.

This thing started life as Spyder Electra DX from roughly 2002. The electronic sear tripper frame was swapped out for an aftermarket single trigger mechanical frame. The valve was "modified" to make it not blow back by adding JB weld to the flat side of the valve stem and was then turned back to round on the lathe, this mostly worked.

There's still a decent amount of gas that escapes around the valve stem so I milled flats in the side of the hammer to reduce blowback, and then eventually I drilled two vent holes on each side of the body just to the rear of the valve body. It's functional but makes quite the fart sound.

The gun actually fires from an open bolt as I left the bolt and hammer connected together, and the decoupling happens via a big slot in the pump rod. The pump rod is attached to the old cocking handle hole in the hammer via a bolt, washer, and a little turned spacer with a shoulder on it. This cocking bolt coming loose is probably the least reliable part of the whole gun.

[RattManDu]

The pump handle is a gigantic piece of solid aluminum, with bronze bushings pressed into it. It rides on the stock expansion chamber that was turned down to make it smooth, And there's a plug pressed into the front end of the expansion chamber with a bolt coming out the bottom. That bolt slides in slot in the bottom of the pump handle and that's what keeps the pump handle from sliding off.

[RattManDu]

The stick feed is a 1" aluminum tube with an .125" wall pressed into a big block that bolts onto the stock feed-neck tapped holes. It does only use the front bolt, but it hasn't broken yet. The feed gate is a purchased delrin piece that's just pressed onto the tube. I think it holds about 15 balls.

[Headshotted]

Do you run it on 12g's or bottle? Really cool either way!

[RattManDu]

I used to run it on a 9oz CO2 bottle, last time out was on a small HPA bottle. It isn't particularly efficient with all the farting so I never tried 12 grams.

[Brianeric26]

Pretty cool im making a spump myself and was wondering why everyone make thier spump closed bolt instead of letting her closed bolt as it was normally, did the closed bolt made anything different other than being easier to build and the vall detents holding the balls ?

[JeeperCreeper]

Closed bolt is easier on paint. Not sure why you would want to make an open bolt. You would have to keep the bolt and hammer connected, and have a pump mechanism that can push them back to cock them, then be able to freely move forward without the bolt. Otherwise your pump would have to move forward with the bolt and that's just silly.

[JeeperCreeper]

Also with closed bolt your detent won't keep the ball in the barrel. You either have to underbore, or make nail polish detents..

Most pumps are closed bolt.

[Altec]

I built a very similar design about the same time. Custom brass hammer, not recocking slot in the valve pin, and I hid a pump handle travel limiter under the side plate to control the pump handle. I got 95% done with it and stopped. Keep saying I’m going to finish it. It works and shots. Just needs the details.