This build is moving forward! After procuring a GI reg, I'm stepping away from the spurt gun in favor of a 25 shot cannon. For the gun, I was going to build a standard gun with a half-unit mag, but decided to use this boat as a test bed for a new cannon design I'm developing. When finished, the gun should reliably fire one bb at a time, period. No tweaking the piston or messing with spring strength here.
How has the testing been going so far? I would be interested in your design as I am building a destroyer as well.
Testing has been going well. Tonight will be the first test with the uptube installed. If it works correctly it should be done. Nice thing about this design is anybody can build one. You just need the printed parts, a few things from McMster-Carr, assemble and you're done, the gun works.
Ok, so your standard Fast Gun cannon has the piston going vertical. When fired, the piston is forced upwards, blocking anymore than one bb from being fired. A spring is used to return the spring to its original position for the next shot. When building guns, it takes a lot of tweaking to get spring length/strength and piston length correct to make the cannon work correctly consistently. This gun eliminates all that. Here are photos of the internal, I'll write up a post explaining how it works.
Ok, lets start from the beginning. After the mag is loaded, two bb's fall into the selector chamber. That is the area between the mag and the cap on the right. There is an O-ring there to keep any more than two bb's from entering the chamber. When the gun is fired, the blast of air is directed at the piston. The piston has an O-ring on it to help it seal against the wall of the selector. The blast of co2 forces the piston forward, pushing one bb though that O-ring mentioned earlier. The bb is then pushed up and out of the gun by the second air port. The piston is limited in travel, so it can only push one bb through the o-ring. The o-ring on the piston prevents co2 from escaping around the piston and forcing more than one bb through the selector O-ring. I hope that made sense to you all. If not, ask me to clarify.
Using the o-ring to keep the BB from entering the breech is genius. I've tried to figure out how to get the piston horizontal and never come up with a solution. Excellent work! You can also substitute a pre-made cylinder like a Clippard MPA-3 or SM-2, eliminating the need for a home made piston.
