$3,375 Electromagnetic Gun Declared “A Serious Weapon” in Expert Range Report | Hacker News Reader

$3,375 Electromagnetic Gun Declared “A Serious Weapon” in Expert Range Report

thedrive.com

15 pointsgraderjs15 comments

On the one hand, i want one and then i want to build a truck mounted version and etc... that looks like fun. "should not be used within 50 feet of anyone with a pacemaker" sounds like more fun than cheap dynamite.

On the other hand, for what it appears to actually do... No, I think I'll stick with my trusty, dusty, Ruger 10/22, thanx. If the job is "punching small holes in things far away" then we have far better ways of doing that. As much fun as this idea is i don't actually see a use for it that isn't better served by other technologies.

"just for the absurd joy of it" is sufficient reason.

There's one more thing, though. This does not meet the legal definition of firearm, and thus could be made fully automatic. I think this adds to its potential for absurd joy.

I think it would be better to use non-magnetic spherical projectiles with a rare earth magnet sled pushing on them.

That might give you better ballistics but would probably come at a cost to reliability and complexity. You'd still need to accelerate the sled to at least the same velocities they're doing now for the slug. Then you'd need to stop the sled in a very short distance which would put forces on the components that aren't there now. Finally, you'd need to reliably return the sled to it's starting position for the next shot. In conventional firearms you can move the bolt backward using either a gas return tube or blowback but those aren't an option for this type of weapon.

You could plausibly run the coils in reverse to pull it back to the beginning, but you'd need to make sure the next round isn't in the way.

Just make it pump-action, it's experimental anyway.

Interesting. Why?

Spherical for the same reason musket balls were spherical - no tumbling = better accuracy.

Strongly magnetic sled for faster acceleration with the same magnetic field in the gun. Also with sled geometry fixed you can change the projectile without changing the coil timings.

Non magnetic ball so it doesn't stick to the sled.

Musket balls are actually horribly inaccurate. Whatever spin that gets imparted on it tends to cause it to fly in a direction due to the Magnus Effect. If you don't impart a known amount of spin and direction of spin, the projectile will get deflected a variable amount in a variable direction. This is why paintballs and airsoft have hop-up: it provide a consistent amount and direction of spin, in a favorable direction to increase range.

Why do musket balls have spin? Because there's space between the ball and the barrel, and as the ball moves down the barrel, in bounces in the space, and every time it hits the wall of the barrel, it ends up getting a bit of spin from that contact.

Curious...going big picture about ballistic projectiles for a moment...what about a hollow-all-the-way-through projectile shaped like a jet engine air intake with "rifling" on the inner side to turn airflow, spiraling the incoming air from the wider "mouth" of the bullet toward a tiny "nozzle" at the rear of the bullet, through which this air is expelled. I'm not physicist-enough to know if this will do anything, but is this in anyway a plausible idea...or just terrible? Happy to learn.

I think what you're effectively looking at is a rifled (Foster) slug. Turns out the rifling on the slug doesn't do much. The majority of the stabilizing effect on a Foster slug is from the fact that the center of gravity is well ahead of the center of pressure.

Having an actual hollow all the way through the slug with rifling would probably have increased air resistance compared to having the rifling on the outside, while rifling on the outside would have better ability to apply torque to the projectile. So knowing that rifling on the outside doesn't work well, we can estimate rifling on the inside would do even worse.

Awesome, thanks! Well was worth a try.. Heh

> Also with sled geometry fixed you can change the projectile without changing the coil timings.

I don't think this is true unless the mass of the projectile is negligible compared to the sled. if so, you are spending most of your energy moving something that does not deliver KE to the target.

or unless all your projectiles have about the same mass, which also seems like an inconvenient constraint.

Might be fun to flip this on its head and make an electromagnetic rocket of some kind.

The simplest idea wouldn't be a real rocket but a pair of coils, some optical sensors, a supercapacitor, and control electronics. It would launch from a rod made of alternating plastic and metal pieces like a stomp rocket.

The more ambitious idea would be to try to build something very small that fires maybe 2mm spheres as propellant. I kindof doubt it's workable.

Please try!

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