A few more updates. I am only a few steps from test phase. I just need to connect pilot to the injector, and then I can begin pressure testing to make sure the piston seals(I'm sure it won't the first go around) and to check for leaks and function. Then the spark rod (Multi-Spark Gap Electrode) will...

I did some tests on the rubber for the sealing face by repeatedly compressing against the metal face. The test pressure was 200 lbs, double what I intend to subject it to. The rubber had a very small groove cut into it but it did not cut any deeper even after several more tests. I plan to round off ...

MrCrowley,

What kind of rubber have you used? I went with EPDM specifically since it has high abrasion resistance and heat resistance.

I had that problem with the weld. If I am assuming right, you are talking about the welded seam in the pipe nipple. I got home from Ace Hardware and opened the package to find a big nasty weld inside that made putting a piston through it impossible. My solution was to go with Black Steel on that fit...

I am hoping to slide the piston into the pilot chamber, and then you can tighten lock nut until it is snug against the metal wall. With the proper lubrication, it might work.

So the assembly is going well so far. It has been difficult to put a lot of work into it lately. Another complication has been the fact that I have just bought a house with a garage, but I have limited tools. All the materials except for the barrel have been bought out, however, I am still lacking a...

Juggernaut: Thank you for the suggestions. For now I will focus on the efficiency of the piston, and I will likely add a spark strip later. I have been debating over that air line running to the pilot. I am planning on using copper tubing, but like you said, I am not sure if can handle the burst pre...

I never thought I would find myself in this discussion, but here I am. Life has been busy, and I have only been able to turn out one project a year or so. Last year was the LRC-425 Tennis Ball Gun. I have grown bored with combustions, and now I feel the urge to shoot a golf ball at Mach 1. Hybrids h...

Here is the updated design. Same design but different aesthetically.[/img]

So this is really old but Mark.F. and I finally got a more accurate measurement of the muzzle velocity (originally estimated at 580 fps). Mark.F. built a basic chronograph and we did several shots at different pressures and got a consistent reading of 830 fps. In a vacuum, it will go about four mile...

Here is the link to the completed product. It shoots very well and performed beyond my expectations. I know it is not the cleanest design, but keep in mind I built this in an apartment with very limited tools and resources. Enjoy!

I just finished buying most of the supplies. Ill post it upon completion. I just wanted opinions is all.

Assuming the atmospheric pressure where you live is 14.5 psi and the volume of your meter is 1.2 cu in. Your pressure should be around 85psi. If you live at a high elevation then reduce the pressure

Hopefully soon to be LRC-425 Chamber: 4"X21" Barrel: 2.5"X66" Flanged Chamber Dual Ignition Metered Propane It has been awhile since I have built one of these but Im taking a semester off from college for work so I got bored. Lets see how four years of college have affected my capabilities. I have f...

Has anyone ever designed "special ammo" for their spudgun? I have come up with a few ideas but I am curious if anyone else has tried it. Kind of like varmint rounds for a spudgun.