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So i found this...

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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So i found this...

Unread postAuthor: Alex345 » Thu Aug 06, 2015 1:22 pm

A friend of mine asked me to cut a .50 bmg bullet down the middle for some kind of artsy stuff he was doing. Bout halfway through cutting my blade hit something VERY hard, i ruined almost 2 blades before giving up and using a dremel to cut away the copper jacket to see what was causing my problems... Didn't take me long to find it;

pic1.jpg
pic1.jpg (31.23 KiB) Viewed 709 times


Sooooow, what to do with this? I'd really like to incorporate it into a sabot round for my upcoming cannon :) It's a 30mm cannon so this should work just nicely on a sub-caliber penetrator! But how would one attach this to a stem with fins? I don't think you can just drill and tap into this stuff?
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Re: So i found this...

Unread postAuthor: Ragnarok » Thu Aug 06, 2015 2:56 pm

This is the basic principle I've used a few times in the past, which can be adjusted to many sub-calibre projectiles fairly easily:

Image

Obviously, it also needs a sabot disk behind the projectile, as it's not in of itself air-tight, but it's relatively lightweight and fairly aerodynamic*.

* When I want them to be more aerodynamic, I make them with a bevelled leading edge and a slightly bevelled tail. Obviously, this reduces the angle on the leading surface (i.e. it's pointier and cuts through the air better), but has a double effect because it also causes the dart to spin, reducing the relative airflow velocity over that surface.
(My best calculations are that the slightly bigger brothers of these darts would go 2.5-3 kilometres if I were trying for range, although it'd be dangerous, unsatisfying and pointless to try).
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Does that thing kinda look like a big cat to you?
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Re: So i found this...

Unread postAuthor: Alex345 » Thu Aug 06, 2015 3:39 pm

Those look nice! What are the fins made of? If i could make something like that i'd still need to attach it to the penetrator itself, and I'm guessing it's tungsten so how would one attach another metal to that? Edit: I think I've read somewhere that silver soldering might work?

How big are those darts exactly?
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Re: So i found this...

Unread postAuthor: Ragnarok » Thu Aug 06, 2015 7:20 pm

The fins there are 2mm polystyrene sheet, variously sold under names like "plasticard" and "sheet styrene". It's not a serious engineering material, but I'm a wargames fanatic and thus have bulk orders of it in different thicknesses because it is good for scratch building vehicles and weapons for models.

Ultimately, I just fixed the fins on with super-glue/kragle/cyanoacrylate/whatever you want to call it. It's strong enough to keep the projectile together during launch (as most of the compression forces are just passed through the fins to the base of the metal core, with little reliance on the shear strength of the glue), fine in flight, and weak enough to break on impact, letting the penetrator core pass through the target unimpeded.

These particular ones are the baby ones, but they still went through 6mm mild steel and several water jugs like a hot knife through butter:



The large white disk you can see come in from the top of the screen, bounce near the left corner of the backstop and head into the tree is the sabot disk that fits behind the projectile. You can see several fragments of fin splashing out from the initial impact, and the core bounces off the backstop to the left. (Actually, if you watch really closely, you can see the core zoom out like a hornet, catch the edge of one of the concrete blocks, bounce back against the water jugs and then fly off at a more sedate velocity).

Those are 75mm masonry nails (with the heads cut down and the points sharpened) about 3.5mm in diameter. The whole assembly is 20mm calibre and about 95mm long.
(The bigger version is basically the same with a 6mm hardened tool steel core instead).

I'm guessing it's tungsten

Well, check with a magnet first, as a lot of AP cores are hardened steel (which can still blunt tool blades, after all, they're hardened steel too), but even if it is, it's still got the potential to be a very mean projectile.

... and a little safer too. Tungsten is rather toxic if you prove to be one of the unlucky people who finds a way to get it into your system... and a skin irritant too, but that's less significant.
In any case, if it does prove to be tungsten, treat it with respect. (Although don't worry yourself unduly about previous exposure - if you weren't suffering from nausea, sudden seizures or a coma shortly afterwards, you probably didn't give yourself acute tungsten poisoning).
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Does that thing kinda look like a big cat to you?
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Re: So i found this...

Unread postAuthor: Brian the brain » Fri Aug 07, 2015 5:08 am

You could determine what it is by weighing it accurately and determine it's volume by measuring waterdisplacement....Hope it's not uranium...
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Re: So i found this...

Unread postAuthor: Alex345 » Fri Aug 07, 2015 1:38 pm

Well, it's magnetic and it won't scratch glass so I'm guessing it's hardened steel :) But yeah you'd need a truly mighty cannon to really use tungsten to it's full potential right?

I'd say these are more then enough for my humble cannon, and my friend told me he's got like 200 of these bullets! They've already been fired out of a gun by the looks of them.

Just a bit bummed about missing out on a free tungsten cutter for my glass rods! :roll:
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