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Poly pipe?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 08, 2008 1:01 pm

Airguns usually use micro-groove rifling, usually 12 shallow groves, as this spreads the stress over a greater area of the relatively soft lead pellet. I would suggest a similar system for spuds.

how much bigger?


Actually 40 cm of 2" tube for a 2 metre barrel sounds about right.
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Unread postAuthor: th3p0p0 » Tue Jan 08, 2008 1:02 pm

I'm not so sure rifling would be entirely effective if you're using taters as projectiles. If you had wax projectiles that could get into the grooves better I'd say yes, but I'm just not so sure about taters






http://www.burntlatke.com/rifle150.html
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Unread postAuthor: ALIHISGREAT » Tue Jan 08, 2008 1:09 pm

th3p0p0 wrote:
I'm not so sure rifling would be entirely effective if you're using taters as projectiles. If you had wax projectiles that could get into the grooves better I'd say yes, but I'm just not so sure about taters






http://www.burntlatke.com/rifle150.html


well it is more effective accuracy-wise but its less effective range-wise. i think that range can be increased by using many shallow grooves and the accuracy can be further increased by using more specialised ammo that will grip the rifling.
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Unread postAuthor: th3p0p0 » Tue Jan 08, 2008 1:18 pm

true. I was just saying that rifling will make a potato more accurate. And that wax ammo sounds like a good idea. Its very soft so the rifling will cut in to it very easy.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 08, 2008 1:21 pm

With rifling, some of the projectile's forward kinetic energy is being converted to rotational energy, so you're obviously going to lose some velocity due to barrel drag - which is why modern anti-tank cannon use smoothbored barrels and fin stabilised rounds ;)
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Unread postAuthor: ALIHISGREAT » Tue Jan 08, 2008 1:23 pm

jackssmirkingrevenge wrote:With rifling, some of the projectile's forward kinetic energy is being converted to rotational energy, so you're obviously going to lose some velocity due to barrel drag - which is why modern anti-tank cannon use smoothbored barrels and fin stabilised rounds ;)


oh yeah! i never looked at it that way :roll: although i would still use micro-rifling as fin stabalized spuds or wax ammo might be a bit challenging :wink:
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 08, 2008 1:39 pm

ALIHISGREAT wrote:oh yeah! i never looked at it that way :roll: although i would still use micro-rifling as fin stabalized spuds or wax ammo might be a bit challenging :wink:


Typical UK thinking, the Brits stuck to their rifled tank barrels longer than any other nation, but have finally seen the light ;) (though the argument was that when firing conventional full calibre shells, the rifled shots were more accurate)
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Unread postAuthor: ALIHISGREAT » Tue Jan 08, 2008 1:48 pm

Typical UK thinking, the Brits stuck to their rifled tank barrels longer than any other nation, but have finally seen the light (though the argument was that when firing conventional full calibre shells, the rifled shots were more accurate)


hmm interesting stuff, but why do we not just use the saboted fin stabalized stuff in the rifled barrels, it would be the best of both worlds, maybe there would be a velocity decrease because of the rifling friction but they could just put a bigger charge in :twisted:
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 08, 2008 1:54 pm

bigger charge = more barrel wear = more expensive = bad news for tight army budgets.

Also, from this excellent article by Tony Williams:

The current state of the art is represented by the APFSDS, or Armour Piercing Fin Stabilised Discarding Sabot shot. This developed because it became apparent that a long thin shot loses less velocity and achieves better penetration than a conventional APDS shot. However, there is a limit to the length of shot which can be stabilised by rifling-induced spinning. It was therefore necessary to introduce tailfins to keep such long projectiles flying towards the target. As the rifling was not required (in fact, it destabilises the long projectiles), smoothbore barrels were developed which also permitted a higher velocity due to less drag. The British have resisted this development because of the resulting loss of accuracy when firing HESH shells, so have retained rifled barrels. Instead, slip rings on the sabot are utilised to minimise the spin rate imparted to the FS projectile. However, 120-125mm smoothbore tank guns have now become standard, achieving muzzle velocities of up to 5,500 fps.
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Unread postAuthor: ALIHISGREAT » Tue Jan 08, 2008 2:00 pm

i will not pretent to know who tony is or will i read the whole article (i'm ment to be doing spanish prep :( ) :wink:

but maybe two guns on one tank is the answer

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like the american Grant which suffered as a result of this because of a massive profile/weight... so maybe its not such a good idea :lol:
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 08, 2008 2:05 pm

The Grant was a terrible idea - ever since saboted high velocity projectiles have been invented, as well as advanced shaped charge and squash head chemical armour piercing projectiles, the ideal tank has a single gun, long enough to give high velocity and wide enough to make its explosive shells effective.
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Unread postAuthor: ALIHISGREAT » Tue Jan 08, 2008 2:11 pm

jackssmirkingrevenge wrote:The Grant was a terrible idea - ever since saboted high velocity projectiles have been invented, as well as advanced shaped charge and squash head chemical armour piercing projectiles, the ideal tank has a single gun, long enough to give high velocity and wide enough to make its explosive shells effective.


well this slightly off topic discussion has inspired me to make a saboted high velocity projectile when i get round to finishing my many other projects :roll: (i'm a notorious non-finisher) so expect to see noobish questions posted about it in the near future :wink:
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 08, 2008 2:18 pm

Well, it's an argument of rifled versus spin stabilised so relevant to some extent.

Saboted darts are great "force multipliers" when it comes to penetration in the sense that they focus the projectiles energy on a very small area, it's the difference between being stepped on my someone wearing stillettos or snow shoes. this is why in spite of their relatively low velocity, Medieval crossbows were capable of bringing down armoured knights.

This is how I managed to penetrate a coin with a needle ;)
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Unread postAuthor: ALIHISGREAT » Tue Jan 08, 2008 2:50 pm

This is how I managed to penetrate a coin with a needle


sounds like something i could boast about to my friends and display like a trophy :D which launcher did you do it with? i might try with my 6mm 'sniper' although at the range i would shoot from it wouldn't be sniperish :lol:
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Unread postAuthor: rna_duelers » Tue Jan 08, 2008 5:33 pm

Using poly pipe is fine,it is rated any were from 15 bar to 22 bar but the stuff you will find at bunnings is mostly around 15-16 region and not to mention it is incredibly easy to rifle.
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