First I must thank everyone for their compliments. On to answering the questions:
Why all the extra distance between the chamber and the darts though?
The extra distance is there only because the bolt takes up that space when it is retracted. It is dead space when shooting though.
How did you test the ranges? Was that a level shot, and was there any dart skip? Does it hurt to get shot from a closer range (say 30')?
Also, do you use all the pressure up in one shot, or does it only let out a little bit of pressure at a time, like in Osiris' homemade?
I tested the ranges by standing in my garage and shooting out towards my neighbors house. I tested the weapon at about 10 to 20 psi (usually 15 psi). To test accuracy, I shot at my neighbor's garage door (about 150 feet away) and repeatably hit it. I shot 3 darts to find out the range. All three soared over my neighbor's house. I went into their backyard and could not find the darts, so I basically assumed that they at least made it to the fence that borders their backyard (the fence that led into their backyard). So I measured out to that fence, and it was 250' and I think 3".
So the gun was able to shoot about 250 max, but that kind of range is completely useless. I was more pleased that it could shoot 150 feet accurately (which is very good).
The gun does not use up all the pressure at one, but I basically was designed to. Because of the semi-automatic valve I put in it, when the trigger is pulled, all of the internals before the pressure chamber are sealed and not used, so only the pressure chamber is emptied.
The pressure chamber that you see takes up about 83% of the volume of the full chamber. All of the stuff before the chamber takes up 17% of the volume. So, you can get 2 shots per tank, one strong one, and one weak one. But I must say that I designed the gun to work with a pressured backpack (just a piece of pipe with an air regulator attached to it).
If you put the pressure up very high (say 40 psi or so) use could get two strong shots if you want, but I prefer low psi. I could modify the gun to allow it to get 4 or 5 shots per tank by extending the area behind the pressure chamber, but this would make the gun even more bulky and huge.
Did you get any inspiration from the FAR that went into the development of this gun?
To tell the truth, yes the FAR did inspire me. I did not like how it was spring powered (no offense), but I loved the rate of fire. So I designed something to offer sort of a compromise between rate of fire and power. So to make it powerful, I made it have a huge (now that I think back, too huge) pressure chamber. The bolt action system fulfills my requirement for fast rate of fire. Also, a fast valve with a large internal diameter was necessary to allow the air to flow better. So I made a homemade semi-auto valve. These fulfilled my goal well.
How many shots can you get from that beast before needing to repump it? And also, couldn't you build a huge magazine with about ten rounds in it?
I could build a magazine that could fit ten rounds, but it would be huge. Plus, it is pretty hard to load rounds into the magazine. I designed my magazine to fit 6, but I have never fit more that 4 in.
Oh, and you used Sch. 80 PVC for the shells, correct?
Yes, just plain pieces of 1/2 inch Schedule 80 PVC. Each is 2 inches long.
Without an ejection system, how do you get the spent shell out? Just let it fall out by tillting the weapon?
The ejection hole is large enough just to remove it with your finger. I was planning on using a standing ejector for it (check the bolt open
picture, look at the mount hole for it), but the plan literally "fell through" (the ejector kept on falling out of the gun). I think that if I redesign the way I attached the standing ejector, I might be able to get it to work again.
What kind of spring did you use for the magazine? Just curious because I know how hard it is to come up with a spring good enough to use for a magazine.
The springs that I used probably aren't what I should have used, but they work well. NerfMonkey asked if I used leaf springs, but I don't think I did. I just went to my local hardware store and bought 4 compression springs. I had to pair them together to get 2 sets of two and they work great.
I am a bit skeptical about your ranges though. 250 feet is a bit high. I beleive there is an asymptotic limit for nerf darts slightly over 200'. I`m not saying you're ranges are BS but the amount of energy it takes to get a nerf dart to 250' is quite high and not attainable by the typcial homemade. How are you measuring your ranges?
It is completely understandable why you say that a 250' is very hard to get, because it is. I think that a normal "stefan" homemade dart would have a limit of about 200'. But I weigh my darts heavily with screws. These heavy darts and the huge pressure chamber must really propel the darts well.
To clear up some confusion, this system can have potentially infinite shots. Right now he has the gun setup to be attached to the air compressor in our garage just like many air powered tools. I plan on letting him use my Constant air pressure water gun's air chambers after I build it - this should provide about 22 liters of compressed air stored at at least 100 PSI. I'd have to do some math to figure out how many shots that would be, but you get the picture.
Well put. The gun was designed to use a compressed air backpack, and I have most of the parts to build a small backpack that could provide 8 to 12 shots (2 to 3 clips). A backpack should be no problem since it is filled with air and therefore not the heaviest thing in the world.
I hope that this answers some questions.