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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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Unread postAuthor: DYI » Thu Sep 27, 2007 7:47 pm

I know that you can shoot through steel plate with a normal steel round, but wouldn't a harder metal reduce the muzzle energy needed for a given round to penetrate? I don't have a whole lot of muzzle energy at my disposal here, no more than 3500 ft/lbs for now, and that's only if I can get it running at full power.

Also, please remember that I have only basic materials and equipment to build this ammo.

@Jack: Do you think that the projectile I described will work, at about 3500 ft/lbs of energy (since the shot will be essentially point blank)?
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 27, 2007 10:28 pm

A hard round which isn't affected by the impact means that all the energy goes into penetrating the target, so it would give you an edge but I don't think it's essential in this case.

I think you have the right idea going for a 1/4" projectile, I would have been comfortable even with 1/8" - the coin-through-needle experiments done recently show that small diameter greatly enhances penetrative power. As you know making a projectile longer increases the weight and therefore the sectional density (which is the crucial factor in this case), but if you keep the same weight and reduce the diameter, you'll also be increasing density ;)

at about 3500 ft/lbs of energy


Don't think in ft/lbs - depending how you distribute the energy, lower ft/lbs does not necessarily mean less penetration. An example I had given here:

A simple comparison is to look at typical airguns in the UK, which are legally limited to the same kintetic energy of 12 ft/lbs.

A typical 0.22 pellet weighing 16 grains travels at 581 fps for 12 ft/lbs.

A typical 0.177 pellet weighing 8 grains travels at 822 fps for 12 ft/lbs.

The 0.177 pellet only has 70% of the momentum of the 0.22 pellet, but will penetrate further by virtue of its higher velocity and smaller diameter.


Velocity is key here, so keeping the overall weight of projectile and sabot as low as possible is essential. You need a high sectional density, but as pointed out above, you can up this without increasing weight. Personally, I would have started my experiments not with rebar but something like 4 inch masonry nails - steel, hardened, pointed, all they need is beheading and fins, sorted :)

For heaven's sake, don't underestimate the capabilities of your projectile and use a decent backstop :shock: :D I saw the sneak preview, looks like it will be up to the task - do keep us posted.
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Unread postAuthor: DYI » Fri Sep 28, 2007 8:20 am

Thanks for all the advice, I'll try to incorporate it all into my design. I have access to steel rod in sizes from 1/8" up to 3/4", so I'll try to make a 1/8" dart.

My backstop is about 1/2 mile of open water, with several miles of uninhabited wilderness behind it, so I won't be hitting anything important if I do shoot through the target.

The sneak preview was the only decent video that I got that entire day, due to camera malfunctions and other problems. I used the rebar because I have loads of it lying around already, not because I thought it was going to work very well.

I'll probably build a bunch of rounds and do some testing to compare penetration on my next shooting day, which might be next weekend.

Also, I have a question: Could the rounds do without fins if the range was point blank (i.e. less than 12" from muzzle)? Just have the sharpened steel rod and a tape sabot that would slide off on impact with the target. If this would work, I could build and test a lot more projectiles.
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 28, 2007 8:27 am

Also, I have a question: Could the rounds do without fins if the range was point blank (i.e. less than 12" from muzzle)?


Yeah it'll be fine.
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Unread postAuthor: Novacastrian » Fri Sep 28, 2007 8:29 am

http://i182.photobucket.com/albums/x281 ... ctiles.jpg

You need a small diametre round with a high speed steel head like these :twisted:

Edit: To do this cheap use an old thread tap- and sharpen it to a fine point.
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Unread postAuthor: Novacastrian » Fri Sep 28, 2007 9:20 am

st.croixsurfer wrote:may i suggest some sort of magnetic explosive round :twisted:


No you may not, explosives are a big no-no here :P

Welcome to spudfiles :D
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Unread postAuthor: DYI » Fri Sep 28, 2007 10:58 am

You need a small diametre round with a high speed steel head like these


That looks impressive, but I don't have the means to make anything like it.

JSR: thanks, this will make the whole process much easier.
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 28, 2007 11:10 am

Novacastrian wrote:http://i182.photobucket.com/albums/x281/Combustation/Projectiles.jpg

You need a small diametre round with a high speed steel head like these :twisted:


You -have- to make a 50 cal version of the round I had suggested here once you get that pneumatic done ;p
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Unread postAuthor: Novacastrian » Fri Sep 28, 2007 5:15 pm

I may make it before i finish the pneumo- i'll test it in my Hybrid after i finish it's reconstruction :P
At 4x evbec estimates 1200fps and 800+ ft lbs. :P
With that sabot design i could go from 23mm to a projectile of say 8-10mm,
if that doesn't penetrate 1/4 " plate it should make a nice dent at least :D
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