Portable 1.25kJ Coilgun

For anyone who doesn't know what a coilgun is, it's a gun that fires a projectile with magnetic force instead of gunpowder. The projectile from this gun won't kill a person, but the electrical energy stored in the capacitors is 78 times the lethal amount for human beings so this is no toy.

Some technical data:

- Action: single stage, bolt
- Weight: 7.75lbs or 3.52kg
- Power supply: 12V NiMH battery (needs recharge after ~15 shots)
- Charging: 40 watt regulated ZVS flyback driver (charge time ~30s)
- Capacitor bank: 4x 3900uF @ 400VDC
- Stored electrical energy: ~1.25kJ
- Switch: SCR
- Body: lightweight ABS plastic pipe and sheets

Performance Data:

- Muzzle velocity: 39.2m/s
- Projectile mass: 32.8g
- Kinetic Energy: 25.20 J
- Output efficiency: 2.02%

Pictures: http://www.youtube.com/watch?v=ovSVYK...
Discuss: http://4hv.org/e107_plugins/forum/for...

***Answers to commonly asked questions***

Q: Will it kill a human?
A: The only ways it will kill is if someone were to touch the capacitors or high voltage charging circuit, which could easily cause electrocution. I suppose if you fired it straight into your stomach or face from point-blank range and refrained from seeking medical attention afterward, you could die that way as well. The muzzle energy of the coilgun is not comparable to regular firearms.

Q: Will a smaller projectile result in better efficiency?
A: No, a smaller projectile won't magnetically couple with the coil as well as a larger projectile will, and won't absorb as much energy. So a small projectile will actually carry much less energy and probably even travel at a lower speed.

Q: Will rifling in the barrel improve accuracy?
A: No- Rifling depends on the bullet expanding within the barrel, which doesn't happen with a magnetically propelled projectile at these speeds.

Q: Will you sell it?
A: Nope, sorry!

Q: Will you post plans?
A: And deprive you of the fun of building your own? Of course not! But I'm willing to point you in the right direction. It's not that hard- I started this project with zero experience with electronics. It takes more patience than anything else.

Q: Will multiple coil stages improve power/efficiency?
A: Yes! I only have one stage on this design for the sake of simplicity.

Q: You should shoot it into some meat!
A: That's a waste of a potential sandwich

Q: What are the songs in this video?
A: In order: Kick It, Rally, and Behemoths from Mechwarrior 4, Invaders by Excision and Datsik, Still Alive by Jonathan Coulton and GlaDOS

Q: How do you claim 1.25kJ of energy?
A: Some websites which feature my gun state that I am delivering as much energy to target as a .45ACP. They are incorrect, either because they didn't read my description or maybe they just didn't fully understand it. 1.25kJ is the ELECTRICAL energy stored in the capacitors, according to the equation E = 0.5*C*V^2. For this gun, C=15600uF and V=400V, thus E = 1248J. One of the main drawbacks for coilguns is EFFICIENCY, which, for single-stage hobbyist designs (like mine) is limited to about 3%. The efficiency of the CG-33 is 2.02%, so the kinetic energy (delivered to target by projectile) is about 25J, which is much more than a bb gun but much less than a real gun.

Q: You misspelled necessity! You suck!
A: I'm SO sorry. How can I possibly make up for for all the pain and distress I've brought into your life?

• Category

  Science & Technology

[TheNightTimeScene]

And a real coilgun shoots 120mm mortar rounds. A hobby-scale railgun should be fine with just using the projectiles as the conductor while not having the rail wear out much (still more than a CG). It gets a bigger advantage from longer rails at the scales you would make them (it's like a cosine function) and could be a nice project for the person who could get this done. I am not asking why CG instead of RG, I am asking why not a RG too?

[Solarenemy1]

A real railgun creates an extreme amount of pressure due to explosive plasma. If you look at vids of the navy's prototype it is built using 3 foot by 2 foot 3 inch thick slabs that are bolted at every two inchs. The gun is about 20 feet long.The rails must be made from a metal that is extremely hard are you will have to change them after 3 or four shots due to erosion from the plasma. Just do a search for the naval railgun and see what goes into a REAL railgun.

[TheNightTimeScene]

Could you elaborate? What kind of more metalwork do railguns need beside two strong rails mounted firmly? I'm confused.

[Solarenemy1]

Railguns are much harder to build. Requires extensive metalwork and machine shop time and is about ten times the cost of a coilgun. For an amateur level there is not much difference in power per size, So a coilgun that is well tuned and optimized is better for a home or should I say an apartment builder.

[TheNightTimeScene]

Why not a railgun?

[Solarenemy1]

He got it on eBay according to a previous post and he even mentions the model number in the video. Er I'm sorry displays it in the video.

[amosjerome]

hi! where do you have buy your SCR. I don't find one...

thank you!

[Temo Saenz]

But will it serve as a good PDW?

[Solarenemy1]

Yes there is recoil. It is strong enough to move the entire weapon slightly. In practice the larger the round, the stronger the recoil.

[Volti102]

Does firing a coil gun like this have a kick back? Do you feel Recoil from firing it? I know its not the same as a regular ballistic bullet but I'm just wondering if the magnetic forces give any kind of push to the user.