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Penetrating 1/4" plate steel

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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Penetrating 1/4" plate steel

Unread postAuthor: DYI » Sun Sep 23, 2007 4:37 pm

As the title suggests, I'm trying to design some sort of ammo to penetrate a 1/4" steel plate that I have and wanted to run my ideas by you guys first before I try it.

I don't have any machining capabilities, so I need this to be relatively simple. Today I tried with a sharpened and saboted piece of 3/8" rebar about 8" long, and weighing around 400 grams. It was fired at point blank range from a 2" barrel at about 430 fps, giving it about 2500 ft/lbs of muzzle energy. The result: the rod was completely blunt after the shot, with pratically no point left, and was fairly warm. It put a tiny dent no more than 1mm deep in the plate. Conclusion: the plate was made out of harder steel than the rebar.

My planned solution is to use saboted 1/4" steel rounds, about 12 long.

I have a few questions: Any ideas how to make fins for the round that won't get sheared off under >2000 Gs of acceleration?

Does anyone know where I can get rods made from either hardened tool steel, or possibly tungsten carbide? I live in Canada, so I can't order from Mcmaster.

Please offer any ideas that you have to improve on this design.
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Unread postAuthor: Hubb » Sun Sep 23, 2007 4:42 pm

First off, the hardened steel or tungsten steel is going to cost you...a lot. However, you may can go to a hardware store and purchase what's called grade 8 bolts (they are hardened steel). I've never seen one as long as you are looking for but it may work.

Also, what are using as the cannon? If not a hybrid, I would suggest a pneumatic with lots of pressure.

It can be done. Good luck.
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Unread postAuthor: MaxuS » Sun Sep 23, 2007 4:48 pm

Why are you using rounds which are 8 or 12 inches long? I would use only around 2" at the most.
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Unread postAuthor: DYI » Sun Sep 23, 2007 4:55 pm

I am using long rounds because of the greater penetration power they offer for a given muzzle energy. Have you ever seen an APFSDS round, or wondered why an arrow is such a disproportionately effective projectile for its velocity and energy? That is the effect I'm going for.

And I know that the hardened steel / tungsten carbide will be expensive, what I want to know is where to get some.

As for what I am using for a cannon, you'll have to wait until I post it to find out.
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Unread postAuthor: Hubb » Sun Sep 23, 2007 4:58 pm

Like I said in my post, check local hardware stores for grade 8 bolts. These bolts have six marks on their heads and are usually a bronze color. They will not be as long as you need but they are bolts, which means you can screw them, or even weld them, together, then sharpen them with a hardened grinding stone.
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Unread postAuthor: Fnord » Sun Sep 23, 2007 5:35 pm

The line between the power of spudguns and traditional firearms is starting to get blurry.

You can harden steel yourself. For a piece of 3/8" rebar, you need to get it glowing bright yellow and dunk it in cold water. Or you could just cut up/sharpen a screwdriver.

Tungsten can be found in furnaces, as it is used for the electrodes in a spark gap.
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Unread postAuthor: DYI » Sun Sep 23, 2007 6:20 pm

The line between the power of spudguns and traditional firearms is starting to get blurry.


When you look at something like FEAR, the SWAT gun, or your 40 foot pneumatic, all with potential muzzle energies of over 10 000 ft/lbs, this doesn't really seem all that powerful that powerful. The real difference is that you can hold a rifle capable of 4000 ft/lbs in your hands, while this launcher takes up, well... a bit more space.

Thanks for the advice on hardening the rebar, I'll try that in tech sometime. A screwdriver or furnace electrode isn't quite big enough for this idea though. Drill blanks might be a good idea though. I'm sure I can get those somehow.
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Unread postAuthor: Killjoy » Sun Sep 23, 2007 7:37 pm

I designed some armor piercing rounds a while back. Basically all it is is some tungston rod encased in steel. You can get tungston rod at most welding shops for welding electrodes (and they are generally 1/4" in diameter).
My plan was to make a mold, center a 3" section of the tungston rod, and use thermite to cast steel around it, and then weld steel fins to the round to stabilize it, and grind the tungston rod to a point. Simple and should be effective. And evrything is pretty easy to get.
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Unread postAuthor: DYI » Sun Sep 23, 2007 7:46 pm

I may try that, I just figure out how to explain to the welding teacher why exactly it is that I'm making a sharpened steel dart...
Any ideas on how to get the entire rod glowing hot so that I can harden it?
And does anyone know where I can get tungsten/tool steel drill blanks in Canada?
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Unread postAuthor: Killjoy » Sun Sep 23, 2007 8:08 pm

Hey I never said it would be easy lol.
Actually if you had the time and the money (for anyone out there), when
I was at caltech for an internship I was working with metalic glass (google it), and the guy I was working with said they had done tests and had found that by encasing a tungston rod in metalic glass, the resulting projectile had the same penetrating ability as a depleted unranium round. Its suprisingly simple to do, relatively cheap, the only problem would be the start up cost for the materials and machines. I might have to try it some day...
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Unread postAuthor: rna_duelers » Sun Sep 23, 2007 8:22 pm

You do realise and M1 Barret Rifle without amour piercing rounds will not penetrate clean through 1/4 steel plate,and that has I believe has a muzzle energy of 16,600 joules/12,200 ft/lbs,with a 45gram projectile.So you need not only high energy but a very hard projectile to actually penetrate the steel.So using extremely hard projectile such as tungsten is on your to do list.
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Unread postAuthor: frankrede » Sun Sep 23, 2007 9:17 pm

Tungsten needle?
That may not help, but this sounds like the job for a large bore sabot+smaller ammo.
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Unread postAuthor: clide » Sun Sep 23, 2007 9:18 pm

DYI wrote:I may try that, I just figure out how to explain to the welding teacher why exactly it is that I'm making a sharpened steel dart...


Custom lawn dart :wink:
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Unread postAuthor: turbohacker » Sun Sep 23, 2007 9:26 pm

Try some 1" steel rod, and harden it. (you will need several rose bud torches to get the entire thing hot)

Then get an ungodly large gun with a 20 ft+ long barrel and hope for the best.
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If it walks like a dog, sratches like a dog, and barks like a dog, than its probobly a...-TURTLE, it's a TURTLE!!! Cant you see?!!!

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Unread postAuthor: Fnord » Sun Sep 23, 2007 9:44 pm

Any ideas on how to get the entire rod glowing hot so that I can harden it?


You can easily get a big piece of steel glowing nicely with a little bit of charcoal and a blowdryer or similar type of fan. I've tempered some sword blade that were 3 feet long, which involved getting the entire length glowing bright orange, though I had to use a funace fan for that.

From what I've found, pluming-grade steel can be made to a wide range of hardness by quenching at different temps. Here's some guidelines:

1000 F (glowing very dull red)- Very soft. won't shatter or crack.

1500 F (brighter red-orange)- decently hard and good for making thick impact resistant tools

1800F (bright orange) Good for knives/swords. Very springy and edge-retaining. Sometimes slightly brittle.

2200F (very bright yellow) Extremely brittle- You can shatter it with a hammer

2500F (White hot) -Starts giving off sparks and dripping beads of molten steel. Will probably shatter/explode when quenched.
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