Fully Automatic
Posted: Wed Oct 18, 2006 10:22 pm
Alright, I started this thing last year and I hit some major problems, but now I really want to finish it, so I'm looking for as much help as I can get. Basically, I'm building a gun to be fully automatic. It runs on a piston-driven blowback system, like that of an AK-47. The explosion pushes a piston in the barrel out, which opens the breach, allowing another round into the barrel, opens the gas, and turns off the spark. Then, a spring pushes the piston back in, closes the breach, turns off the gas, and hits the spark, firing another round and starting the process over again. It will (probably) have a gravity fed, open ended magazine. I'm running the gun off of propane and oxygen, and will have a sealed and semi-pressurized chamber. The ignition will be from a spark plug out of a car, running on a 12 volt car battery. The gun is made from PVC, and has a 4 inch, 2 foot long chamber, and a 1 1/2 inch, 4 foot long barrel. I'm not firing potatoes because you can't get them in a uniform size without spending way too much time carving them. Instead, I'm taking ping-pong balls and using a needle and syringe to inject them with water, then freezing them. So I suppose it is less of a spud gun, and more of an ice ball gun.
If I lost anyone in that description:
http://www.putfile.com/pic.php?img=3744986
http://www.putfile.com/pic.php?img=3744985
That is a picture of the gun last year when I sort of gave up on it, as well as my original plans. In the picture, I only have the propane installed, and have none of the mechanical systems working. The pipe coming out the top is the "magazine." I fill it with balls, and they drop into the barrel, right in front of the chamber. It is hard to see in that picture, but there is a hole in the top of the barrel, and a slide that covers it. The pipe on the bottom is the piston. I currently have it cut to half that length, and used small steel bars to hook everything up.
So now that I have explained what I have done so far, I'll get to the problems and pray that one of you can help me. I suppose the most prevalent problem would be the fact that when I open the breach, one ball drops into place, but then there is absolutely nothing stopping it from rolling along the barrel and allowing another ball in. This would be fine if I wanted to fire 2 balls at once, however the second ball tends to get jammed as the slide closes over the breach. Any ideas on how to only let one ball in at a time would be great.
The second problem is that when I turn on the propane and oxygen, I don't think they will have time to mix and fill the entire chamber during automatic firing. I've heard about having a fan in the chamber, but I'm not sure how that works and if it would help me at all.
I'm sure I have more problems that that, but those are the two that are giving me the most trouble. Any feedback and/or ideas would be great.
If I lost anyone in that description:
http://www.putfile.com/pic.php?img=3744986
http://www.putfile.com/pic.php?img=3744985
That is a picture of the gun last year when I sort of gave up on it, as well as my original plans. In the picture, I only have the propane installed, and have none of the mechanical systems working. The pipe coming out the top is the "magazine." I fill it with balls, and they drop into the barrel, right in front of the chamber. It is hard to see in that picture, but there is a hole in the top of the barrel, and a slide that covers it. The pipe on the bottom is the piston. I currently have it cut to half that length, and used small steel bars to hook everything up.
So now that I have explained what I have done so far, I'll get to the problems and pray that one of you can help me. I suppose the most prevalent problem would be the fact that when I open the breach, one ball drops into place, but then there is absolutely nothing stopping it from rolling along the barrel and allowing another ball in. This would be fine if I wanted to fire 2 balls at once, however the second ball tends to get jammed as the slide closes over the breach. Any ideas on how to only let one ball in at a time would be great.
The second problem is that when I turn on the propane and oxygen, I don't think they will have time to mix and fill the entire chamber during automatic firing. I've heard about having a fan in the chamber, but I'm not sure how that works and if it would help me at all.
I'm sure I have more problems that that, but those are the two that are giving me the most trouble. Any feedback and/or ideas would be great.