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spudgun range, are we falling short?

A place to ask general spud cannon related questions.
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Unread postAuthor: JDP12 » Sun Apr 03, 2011 8:47 pm

sorry.. maybe I missed something. What are the sabot "pins" for? What's wrong with a traditional sabot design, possibly with a cylinder of some hard material behind it to ensure no gas seeps past?
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Unread postAuthor: jor2daje » Sun Apr 03, 2011 10:26 pm

so i tested my first design after I welded three fins onto the back, I turned a sabot from a couple different pieces of pvc. Performance was disappointing, I couldnt get a good highspeed because of the short range and poor weather, but I could tell from the target that it hit sideways. This is probably due to the pretty heavy fins, bad cg, and ineffective sabot design.

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So I took it a new direction and decided to turn a massive slug. Its 320 grams turned from from 1" steel about 2" long. It comes down to a 3/4" at the back so it is a tight press fit into the yellow reducers that I turned to make a perfect fit in my barrel. Ill have to wait until tomorrow to fire this, and while I doubt range will be that impressive I think damage should be quite awesome.

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Unread postAuthor: LeMaudit » Sun Apr 03, 2011 10:47 pm

JDP12 wrote:sorry.. maybe I missed something. What are the sabot "pins" for? What's wrong with a traditional sabot design, possibly with a cylinder of some hard material behind it to ensure no gas seeps past?


The idea is to let some hot gas from the hybrid reach the holes of the tail and go inside. So it cannot be a back cylinder. I'n not sure what you call a traditional sabot. This design is the same idea as a Spindle Sabot (#4)

The pins serve as a locking point so the sabot can drag the shell out of the barrel. Then the 4 parts of the sabot separate, and because they are designed very light, they should not go far. I may add a backing plate in brass so the heat doesn't melt the UHMW, following MrCrowley concerns about that particular point.

jor2daje wrote:so i tested my first design


Interesting! But I'm guessing here that the symmetry and surface should be perfect, otherwise it will not flight strait. Also, maybe your tail is not light enough, and the fins too small.
I'm also betting this last slug will do some significant damage :lol:
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Unread postAuthor: jor2daje » Sun Apr 03, 2011 10:55 pm

I'm also working on a design the same size as the first but with a 1.5" long nose of 5/8 steel then a 5" tail made from thin wall 6mm aluminum tubing with either dart flights for fins or I may try to borrow a friends tig and do some thin aluminum fins.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 03, 2011 11:10 pm

Ragnarok wrote:Line of sight techniques like flares, LEDs, etc... they won't work.

If you've got a projectile that's been going fast and aerodynamic enough to travel kilometres, it will just hit the ground and go straight down through it. You'll be digging it out again.


I have that same feeling.

Performance was disappointing, I couldnt get a good highspeed because of the short range and poor weather, but I could tell from the target that it hit sideways. This is probably due to the pretty heavy fins, bad cg, and ineffective sabot design.


Shame, I have a feeling it was that last factor that is to blame.

Again, this is why I am a fan of this design. The sabot only needs to be a wad that seals off the barrel and the projectile is centred by its fins. I might make some small scale versions for my 3/4" hybrid and do some AP testing.

So I took it a new direction and decided to turn a massive slug. Its 320 grams turned from from 1" steel about 2" long. It comes down to a 3/4" at the back so it is a tight press fit into the yellow reducers that I turned to make a perfect fit in my barrel.


Did you hollow out the tail in order to get the CG forward?
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Unread postAuthor: JDP12 » Sun Apr 03, 2011 11:15 pm

ah.. gotcha now. I'm familiar with that diagram.. didn't know you were having the holes act as the "spindle design" depicted.

as far as sabot materials.. anyone considered wood? There are many lightweight woods out there, balsa in particular, and even other woods. its incredibly easy to turn on a lathe.. Seems like a good idea.
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Unread postAuthor: Lockednloaded » Sun Apr 03, 2011 11:20 pm

JDP12 wrote:as far as sabot materials.. anyone considered wood? There are many lightweight woods out there, balsa in particular, and even other woods. its incredibly easy to turn on a lathe.. Seems like a good idea.


Also, I feel like a strong metal nose with a replaceable screw-in wooden tail would work very well
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 03, 2011 11:26 pm

JDP12 wrote:as far as sabot materials.. anyone considered wood? There are many lightweight woods out there, balsa in particular, and even other woods. its incredibly easy to turn on a lathe.. Seems like a good idea.


Gerald Bull agrees with you ;)
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Unread postAuthor: JDP12 » Sun Apr 03, 2011 11:38 pm

cool...

So lets see some wood sabots! When i get home I may actually make some.. balsa seems like a very good candidate.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 12:35 am

JDP12 wrote:balsa seems like a very good candidate.


It is, in my very early days when all I had was an airsoft springer I remember making balsa sabots to shoot individual lead shot :)
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Unread postAuthor: MrCrowley » Mon Apr 04, 2011 4:29 am

Just had a brain fart this very moment (so forgive me if the idea is a bit daft), but what if the projectile was filled with a dye (biodegradable and non-toxic of course) and in the tail section was a very small nozzle that controlled flow. I'm not sure if there would be any "suction" type effect at the rear of the tail that would leak the dye or if it would do it naturally or whether you'd need holes at the front of the dye cavity so air could push it out.

Just thinking it might leave a rough trail on the beach, and by trail I mean random splashes of dots at random intervals. Wind would have a huge effect and push the dye off-target but I think it would help enormously if it actually worked. You could probably narrow down the impact zone to 100 squared meters or so.

Ok the idea seems really daft now that I've explained it but in the small chance that it's actually brilliant, I'm going to click "submit" :D
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 4:51 am

Not as silly an idea as you think. If I remember well according to one of my Ian Hogg books, before pyrotechnic tracers they used a liquid dye that would be leaked out by the centrifugal force of the spinning bullet, when I get home I'll give you the exact quote.

As to actually leaving a trail on the beach, I wouldn't be too optimistic. It will be too dispersed to be visible.
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Unread postAuthor: CpTn_lAw » Mon Apr 04, 2011 5:03 am

Why did anybody think about saboting a crossbow dart? Fit them with lumenoks and there you go : tracer spudgun round?
Imagine shooting them from a hybrid? Supersonic, very aerodynamic,fin stabilized....
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 5:09 am

CpTn_lAw wrote:Fit them with lumenoks


Damn,ready made tracers! Why didn't you tell us before :D
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Unread postAuthor: MrCrowley » Mon Apr 04, 2011 5:32 am

CpTn_lAw wrote:Why did anybody think about saboting a crossbow dart? Fit them with lumenoks and there you go : tracer spudgun round?
Imagine shooting them from a hybrid? Supersonic, very aerodynamic,fin stabilized....

Don't think they're heavy enough. I couldn't find a solid number on an arrow's Cd so I used 0.03 which I found some place and the range of an arrow improved from 1800m to over 4000m by increasing the weight from about 25g to 80g.


@JSR,

I remember a few pages ago you were comparing projectile density at 1000fps and noted how a smaller, more dense, projectile went much further than a larger one which weighed the same. I was wondering how you modelled that in GGDT/HGDT since if you put the bore diameter for the 20mm projectile at 20mm, you're not including the extra force exerted on the projectile by a sabot in a 42.3mm barrel but if you put 20mm as the projectile diameter with a 42.3mm bore, it will calculate for massive projectile blowby.

Basically I'm wondering how to differentiate between a 20mm sabot-ed projectile in a 42.3mm barrel and, say, a 35mm sabot-ed projectile in a 42.3mm barrel.

_____________________________________________
I ran some numbers for a 0.25" diameter dart weighing 100g (using a tungsten core it would be shorter than a foot) fired at a very feasible (using a sabot) 850 feet per second and with an achievable CD of 0.1, and GGDT suggested a range of no less than 6207 metres - over three and a half miles!

Can we make this, please? Pretty please with a cherry on top? :D
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