How does a Pump Spyder work?
Let's discuss how this particular style of pump marker actually works in my way of thinking. (Note, there are other styles of pump markers, but I won't address them here.)
Basically, when you "pump", or pull, the handle back towards the marker, a rod attached to the handle and the bolt pushes the bolt and hammer (striker) back until the hammer is locked on top of a sear. At the same time, by moving backward the bolt allows a paintball to drop into the breech, then moves, independently of the striker, back to the forward position and closes off the breech (by way of a return spring of some sort.) This is called a "closed-bolt system". An "open-bolt system" is when the bolt stays back in the gun leaving the breech open and moves forward when the gun is fired, then back again. When the trigger is pulled, the sear is temporarily dropped allowing the hammer to slam forward, hitting the valve pin which pushes the cupseal away from the valve and lets a burst of air into the gun. This air is dirrected through the body, up into the bolt and pushes the ball out of the gun through the barrel.
Here is an animation for you (thanks to zdspb.com) that illustrates how this works.
As you can see in the animation, just like a semi Spyder, it's got a valve, pin and cup seal, a striker and a bolt. The main difference between the two different markers is that it requires a manual operation to get hammer reset for the next shot because the blow back has been disabled. (Blow back is when the striker is "blown back" into the cocked position by air that is directed for that very purpose through the valve, creating a semi-auto operation.)
Check out your gun before you start
Before you start, you need to have a plan. Mainly, you need to decide how the pump handle is going to be attached to the striker or the bolt to accomplish the smooth pump stroke to get your marker pumped quickly and easily for fast (ish) shooting.
There are a couple of different ways, and a couple of different theories, on how to make an easy connection between the pump handle and the firing mechanism. One way is to leave the blowback enabled and just disengage the bolt from the striker. When the marker is fired, the striker "blows back" into firing position, but the bolt remains forward until you pump it back and load another paintball. Sure, that would be easy, but it's not a "TRUE" pump in the way I described above. I'm only going to focus on what I consider the "true" pump method as described above.
So, how are you going to connect the pump to the firing mechanism? Look at your marker. Can you see the back of the bolt? If so, you can attach the pump rod quite easily to the back of the bolt. Is the bolt completely enclosed in the gun? My Sonix was. It wasn't possible to see any of the bolt on the outside of the marker body. So, my options were simple. 1.) Either I had to take the pump arm all the way behind the gun, attach it to a back plate of some sort and attach another rod to the back of the bolt and to the plate. Or, 2.) I could cut a slot in the side of the body to attach the pump rod directly to the bolt.
If your body style is the same as mine, these are the options you have. A lot of the Spyder bodies, though, have a "vision" cocking system, or a window cut in the side of the body so you can grasp the bolt and cock it. Some even have most of the back of the top tube cut off so that makes it even more simple. With these body styles, it'll be MUCH easier attaching the pump arm to the bolt.
I decided since I had the closed body style, I was going to go with option 2 and cut a slot into the side of the body, hopefully giving it a clean, professional-looking finish. That's how I went, and will illustrate in this tutorial. If your body is the other style, you can still follow this tutorial, just skip the body milling part!