Making a Paintball Gun From Scratch – Still building… 

Following the first day of work, we had nearly completed both the bolt and the charge chamber, and had completed the boltstop. In this session we needed to finish up these parts and create the firing chamber.  Brian and I had high hopes going in to this session. He was confident that we would at least fire a shot by the time I had to head home. I was somewhat skeptical! Although we were interrupted by some thermite and Doctor Mario, we were able to achieve this goal.

We did the usual shaping and machining to get the firing chamber roughed out and then got on to the fun stuff… threading. Three parts needed threads. The firing chamber and charge chamber had to thread together at the middle of the gun; and we had to thread the inside of the front end of the firing chamber in order to put one of our Spyder barrels into it. The charge/firing chamber threads would be somewhat simple, as they only have to match each other and require no standardized dimensions. The barrel, on the other hand, has its own thread type that we would have to match. Just to make things more fun, The threads were metric, (M22 x 1.5) and our thread turning gears were standard. Brian worked his magic and got something pretty close to the barrel (7/8 x 16) and we went with it.

External Firing Chamber Threads

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Internal Barrel Threads

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Whole Firing Chamber

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And I have saved the internal threads from the charge chamber for last to present you with a conversation that took place just moments prior to the cutting of the first internal threads we had done.

Joe and I: “Brian are you sure you want to do this without a practice run or anything?”

Brian: “I know what I am doing.”

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He apparently wanted our threads to look like the mouth of the Kraken, but as long as he knew what he was doing, who were we to question him! 🙂

The embedded video shows our first paintball break on target.

Gun air rig sketch

The graphic above shows the air system we had set up when we fired the gun. Constant pressure is supplied to the firing pressure input, where the pressurized air waits to be released and force the ball from the gun. The bolt is held back by air pressure from the trigger pressure input. Whenever the air gun valve is open, this pressure is supposed to be keeping the bolt to the rear and keeping the gun from firing. Whenever this pressure is released (the air gun is pulled away from the input) the firing pressure should cause the bolt to move forward and the gun should fire. This wasn’t happening for us due to what we speculate to be general surface finish and O-ring fitting issues. With some further work and refinement this should be fixable. We ended up poking the back end of the bolt with random stuff and that provided the motivation required to start the firing cycle.