Carnage! Updated (with more videos)

DYI · Tue Aug 07, 2007 3:21 pm

Just to start off, if any mods think that this should be moved to the showcase, feel free to do so, as I had a hard time deciding where to put it.

Well, this afternoon I was bored, and looking for something to do. I remembered that I still had two 1.5", 16 layer alu. foil burst disks, and decided to bring out my SCTBDC, hook on the 12' barrel, and take a shot.

I needed something to shoot (and some ammo), and I found 2 sheets of 5/8" MDF, which I nailed together with spacers to created a 2" gap in between. For ammo, I used a 300 gram piece of wooden dowel that was 16" long, with no modification except tape to help it fit better. GGDT said that this should achieve about 330fps and 1130 ft/lbs of muzzle energy. For wadding I used a ball abou 1 3/4" in diameter made of a foam like material which sealed the barrel very well.

I loaded the gun, set up the target 5' from the muzzle, charged it to 160psi, and vented the secondary chamber... Nothing happened. I waited for a while and, as I was about to go refill the secondary chamber and try again, the gun fired. The recoil was massive enough to throw the whole 25+ pound weight of the gun and barrel 2 feet back and off the stand.

For a few seconds I was preoccupied with a 12' length of ABS pipe swinging haphazardly through the air, at some points bending almost 90 degrees. I didn't take a picture of the gun immediately after the firing because I didn't want to bend the barrel any more than necessary.

After I reassembled the firing area, I went to see what kind of damage this had done.

Since pictures are worth a thousand words, and this post is already long enough, I will use the pictures I took to explain what happened. I really had no idea that this projectile (1.8 square inch surface area on nose) could achieve such penetration. Please note that all of this damage was inflicted with a single shot from a blunt projectile. For some reason the pictures are showing out of order, but it shouldn't be too confusing.

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potatoflinger · Tue Aug 07, 2007 3:33 pm

That's an awesome amount of power, how far is it from where you shot the gun from to the wall that the dowel got stuck in?

Redcoat · Tue Aug 07, 2007 3:51 pm

THat is a great gun.I take it the abnormally long barrel is for higher velocity.
THat dowel rod damage is awesome

.

Looks like a lot of time and work went into this.Nice Job.

Happy Spuddin'

jackssmirkingrevenge · Tue Aug 07, 2007 3:52 pm

Fork in hell!

One of the fundamental rules of gun safety - particularly with unpredictable homemade launchers - is never underestimate the penetrative power of your launcher, and always have an appropriate backstop.

I'm guessing you'll be a bit more careful next time

dauphinoise potato · Tue Aug 07, 2007 4:00 pm

That's carnigerous

DYI · Tue Aug 07, 2007 4:20 pm

@potatoflinger: it is more than thirty feet from the muzzle to the wall, and it became embedded in the wall after being knocked off course from penetrating the tub
@jack: yeah... I'll be using a fairly substantial backstop made out of under padding from a car now. As for unpredictable, I actually ran the stats for this ammo through GGDT before I tested it. It had about 50 ft/lbs more muzzle energy, and 50fps lower velocity than a purpose built penetrating ammo I use (see GEN3 dart in the SCTBDC topic), which is stopped completely by (but still penetrates) a 2" thick solid board. The problem is that, at the time, I forgot that this was only a 80 psi, which probably explains why the power at 160psi seemed so abnormally high.

I don't really think that "carnigerous" is a word, but it certainly sounds impressive.

The C:B ratio with this barrel is about .25:1, and it allows a large amount of the available power to be transferred to the ammo. It is kind of awkward though.

jackssmirkingrevenge · Tue Aug 07, 2007 4:34 pm

GGDT said that this should achieve about 330fps and 1130 ft/lbs of muzzle energy.

Considering an 0.44 magnum round screams through the air carrying just under 800 ft/lbs, and your average M16 generates almost 1,300 ft/lbs at the muzzle, surely those sort of predicted figures should have suggested that more substantial backstop was in order?

dauphinoise potato · Tue Aug 07, 2007 4:39 pm

I don't really think that "carnigerous" is a word, but it certainly sounds impressive.

Yeah it does!

DYI · Tue Aug 07, 2007 4:48 pm

When you think about it as compared to those figures, yeah, it would seem as though I should have realised that I needed a good back stop.

Well, hindsight is always 20/20, and I will obviously be using a strong backstop in the future, but this is a good demonstration of the energy involved. However, and M16 round has a MUCH smaller surface area on the nose, is made of a harder material, has a far higher cross sectional density than this dowel, and a velocity about 9 times higher, all of which make it far more aerodynamic and much better for penetration than my ammo. But you are right, one should always use more safety than is absolutely needed.

jimmy101 · Tue Aug 07, 2007 6:15 pm

Damn.

Never let anybody call a spud gun a "toy".

SnowFlox · Tue Aug 07, 2007 7:13 pm

holy crap !! you can pierce almost a body of a tank !

noname · Tue Aug 07, 2007 7:28 pm

Burst disc guns are fun like that, how you can pressurize it, and then it'll go off totally unexpectedly five minutes later. They're also a bunch more powerful than people think they would be.

DYI · Tue Aug 07, 2007 8:16 pm

Well, this was actually a triggered burst disk, but the disk was too strong (14 layer would be better, but, with a bit of thought, you can see why a 14 layer disk would take longer to make than a 16 layer). I've never had a delay of 5 minutes, but some of them take a long time. You can speed up the process by repeatedly pressurising and venting the secondary chamber, subjecting the disks to more stress. Unfortunately, its kind of scary to be near this when it fires, due to the recoil. I will make a stand at some point.

@Noname: I really need to find a way to get this up to 300+ psi like you did with yours. GGDT says that at 350psi I could get the dowel up to 488fps, and that it would have >2400 ft/lbs of force.

I may update this thread sometime tomorrow with a video of firing a massive ice slug at this same target (with a STRONG backstop).

jackssmirkingrevenge · Wed Aug 08, 2007 1:10 am

SnowFlox wrote:holy crap !! you can pierce almost a body of a tank !

It'll take more than a subsonic broomstick to pierce 12 inches of layered steel, depleted uranium and ceramic

let's take for example the US Army's, solution to the problem, the M829 kinetic energy penetrator - that leaves the barrel at over 5 times the speed of sound with a whopping 4,391,500 ft/lbs

However, and M16 round has a MUCH smaller surface area on the nose, is made of a harder material, has a far higher cross sectional density than this dowel, and a velocity about 9 times higher, all of which make it far more aerodynamic and much better for penetration than my ammo.

Fair enough, but then again an M16 round it would also have gone through your car, and the back end of your shed, etc

DYI · Wed Aug 08, 2007 8:03 pm

that leaves the barrel at over 5 times the speed of sound with a whopping 4,391,500 ft/lbs

The round must weigh over 8 pounds then?

What the hell do they fire that thing out of?

I wonder what kind of damage THAT could do to your shed

... and the shed behind it, and the house behind that, and the car behind that, and the fence behind that...

As a result of some quick (and very inaccurate) GGDT figures asuming 4000 bar hydrogen at about 10 000 degrees fahrenheit, it looks like it's in the neighbourhood of what a large Light Gas Gun could do.

About the ice slug video, it won't happen till tomorrow due to delays caused by an ongoing steam cannon project that isn't working at all.

Carnage! Updated (with more videos)

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