ive built a few and am currently working on an automated one that senses motion and tracks and then shoots the target. if you dont know what a coilgun is, it uses a electromagnet to fire a projectile. a railgun uses two rails instead.
and shoots plasma.
what did you use to make your coilgun?
my friend has always used a disposable camera charger circuit and a cap bank…
yeah im using a cap bank from disposables as well. around 4 caps so in the vicinity of 1200v. my current one is pissweak cause im using 7mm bbs. i wanna make a better one that shoots nails but im having trouble with a loading mechanism because its supposed to be automated and i only have 2 motors to work with. so only one can be used to fire & load. and one for left/right movement. i should just give up and make a handheld one. a robotic one does have more “mad scientist” factor tho. ive found some large caps (coke can sized) but their like $40AUD
I read an article on wikipedia. Sounds fun. How do you make the coils to turn on in the right time order? And what wire do you use for a coil?
We tried making one at school, we had a 1 tesla (yeah i said one tesla) ferrous magnet knocking around and a 400 amp psu. Unfortunately when physics wokred out what we were planning we got stopped. This would have worked on a slightly different basis to your it would seem, our railgun was designed to pass a huge current through a disk in the presence of an enormous magnetic field, thus causing collosal force. Sounds like your is a electromagent which is turned on at the right moment.
i make single coil ones. but trial and error works. atm im wondering if you could use the magnetism from the coil to move a bolt to let the next bullet in. sorta like the recoil reloading mechanism used in some automatics. all the ones ive seen use a bolt action doodad.
this wouldnt help with the chargin time issues tho.
id love to make one so huge it had multiple coils along the barrel so one coil set the projectile in motion, then 10cm down the barrel, the next coil kicks in to accelerate the projectile even more, but is timed to turn off just as the projectile passes it, thus giving an acceleration boost…
also, one so huge it could shoot a slug the size of a CO^2 canister and has to be charged via mains power (a man can dream…)
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for now I’m sticking to PVC air guns. my friend and myself made a top airgun that we named “Doris Mark II” (the first one was combustion powered and only ever got off one good shot) DorisII used a hand held garden sprayer tank as the air reservoir and a solenoid sprinkler valve as a trigger. the solenoid was triggered by a battery and switch, so it was a pretty legitimate and quick firing triggering mechanism. we put a hole in my aluminum fence with that gun 
the slug was a screw in a sabot of foam. god i love that gun, too bad we don’t know the top safe P.S.I and the solenoid screws up so were going to do a rethink for Doris Mark III
happy shooting lads
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indeed you could switch the polarity as it passed so it pushes the projectile as it moves away.
id like to do a multicoil one but id need to make a timing switch thingy with a 555. probs not too hard but still annoying. i was gonna make a paintball marker but decided it was too complex and dangerous. coilguns are reasonably safe provided their electronics is enclosed.
but for that to work perfectly, wouldn’t the projectile need to be a permanent magnet? instead of just a slug (ball bearing, round steel stock… a nail :D)
yeah, and that wouldnt work.
good point, what was i thinking? 
my dad had th same idea with the magnet, so your not the only one.
Not necessarily… as long as it is a ferromagnetic material of some sort, the projectile is partially magnetized when exposed to the initial magnetic field (a phenomenon known as hysteresis).
Yes, it wouldn’t accelerate as quickly as a permanent magnet might, but it’d still work fairly well if done right.