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Comment by junto | Hacker News Reader

I imagine that someone is going to have a visit by the FBI.

That or a job offer.

Is it illegal in the US to build your own railgun? I know that in Germany there is a limit on the Joules you can put in a projectile without a licence, I think something like 8 Joules. This gun would violate that, I guess.

Applied strictly, this probably means that some Olympic sports require a license (hammer throw, discus throw, shot put and javelin)

And of course also Icehockey,Football and a lot more. The german law is bit more specific about it (the exact amount of Joule is 7.5) http://www.dsb.de/media/PDF/Recht/Waffenrecht/Verwaltungsvor... e.g. the weapon/weaponlikethingy must have a muzzle. Also the Intention of usage is considered, so if you produce a hammer with the sole purpose to throw it at me, if may offend German law.

8 Joules is a really small amount of energy. I wouldn't be surprised if an average healthy child could put that much energy into a ball by kicking it. A quick back-of-envelope calculation says a 0.45kg ball (FIFA standard ball) traveling at 6m/s (~13MPH) has more than 8 Joules of energy.

Then again, a ball is an awfully heavy and big projectile.

I'm pretty sure carrying a javelin around in Germany gets you in trouble. The police can get you in trouble for carrying around pocket knives if the blade is too long or locking.

My brother used to carry gladius (in a pouch, on his back, to and from training). No cop stopped him to ask about it, ever.

Just like cops rarely stop you if you're cycling without lights after dark. If they have a reason not to like you they can still use that to slap a fine on you.

However, I'm pretty sure if he'd started waving it at people in the street they'd have become quite a bit less lenient about the fact he was carrying a weapon around.

In the reddit thread [1] the creator mentions many times he asked the BATF it what he was doing was OK, and they never replied. He's confident there is no law against electromagnetic weapons.

He also mentions he's an engineer and has designed/built weapons that have actually been used lethally, so I get the feeling he knows what's he's talking about, professionally.

[1] https://www.reddit.com/r/DIY/comments/3s4o4j/diy_250_lb_gian...

Judging from the size of his projectiles, the bore of his device is almost certainly over 12.7mm in "diameter" (it's square, not round, but it looks to be 0.5" by 1", and I'm not about to leave the hairsplitting to a federal bureau). Classification of a "destructive device" doesn't really care what type of propellant is used. I think it's pretty clear what he has here would be considered a "destructive device". It'll depend on his state whether or not it's legal for him to have.

https://en.wikipedia.org/wiki/Destructive_device

It would put interesting spin on the second amendment fights though.

There was floating on internet a very old post about how to make a railgun, made by a Brazillian guy... he DID got a job offer, but the superiors of those that tried to hire him shut it down because he was Brazillian (he was a Brazillian living in US, he wasn't allowed to legally make weapons for the government, at least for whoever tried to hire him, I don't remember anymore what department it was)

This or any extremist group ...

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