SpudFiles

@Ramses: I planned on having my friend(certified welder) weld the spark plug into the chamber along with the rest of the injector, so I don't have to worry about any threaded parts.

As for the fuel meter I don't have any parts, but I do plan on making it detachable(so I can use it on my other potato guns). I might post a diagram in a little bit for the design. Do you know if I can just buy a propane tank adapter?

If you know anything I could just find lying around that would make a sturdy enclosure please let me know, it would help very much, and I wouldn't have to buy any acrylic.

As for projectiles, probably .25"x.25x1"or.5" pieces of 6061 aluminum or plastic(teflon maybe?) wrapped on one side with aluminum foil, yay plasma. But if I could find where to obtain that copper/carbon alloy I would into that too. On the note of projectiles I was thinking of maybe using lubrication graphite powder on them to increase efficiency, I need to look into that. Maybe even graphite projectiles.

@rp181: The fiberglass is build the enclosure, which should measure 2.25"x1.25"x6', the smallest sheet of fiberglass for the top was 3", so I just decided on a 6" wide piece so I only had to buy one. And the teflon is for the injector rails, and 12" is the smallest width for the 36" of teflon I need, but I'm sure I'll find something to do with the extra teflon. I could make rounds out of the extra fiberglass and teflon.

Do you think the fllowing would make a good charger?
A variac, two radioshack transformers and a diode bridge?

Back to the original point....
That is WAY too long, it will decrease performance from friction. A person I know used a 1 foot long barrel, with 20kJ, more than twice what you are using. Stick with 2 feet, or 3 feet. Your cross section is also overkill, try and calculate the forces, don't just guess.

The barrel of the railgun is 3', the injector barrel is 3', but they are both in the same enclosure.

Still.... You need less than 6" of rails to empty all the energy. You are making the injector too powerfull, you will have a railgun agumneted cannon, not the opposite. For my injection, I use 60 PSI and a burst disc, with the friction, the projectile stops right at the end of the rails. Go with 1-2 foot injection, and 1 foot rail's. The mcmaster part 6" wide .5" x 3' GP03 is perfect.

What science fair is this for?

Frankly, I do not think you did enough research. I did research for nearly a year, and it helps. Hold off the project and do some research.