Fin stabilized smooth bore sabot slug?


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Blakenzy
November 10, 2009, 02:36 PM
I saw one in a catalog a looong time ago. It looked like a ribbed dart in a sabot, minus the sharp tip. I think the brand was Sauvestre or something like that, but I have never seen one in real life, nor any where else. I guess the idea of fin stabilized projectiles fired from smooth bores works well enough that it is used in main battle tanks. Why isn't it more popular with shotguns?

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highorder
November 10, 2009, 02:37 PM
Because fin stabilized projectiles dont have the mass that a sabot or rifled slug does. Mass conveys energy to the target. Finned projectiles are meant as high velocity penetrators.

Slugs are for killing animals, not penetrating armor.

Dr. Tad Hussein Winslow
November 10, 2009, 02:59 PM
Why isn't it more popular with shotguns?

I think mainly because:

(a) in order for a gas seal to form, the fins must be folded or retracted in some manner while going down the bore - such a design is EXPENSIVE to produce, and
(b) Most people that use shotguns for game hunting do so ONLY because their states are "shotgun-only" big game hunting states - well, since most if not all of these states DO allow a "rifled shotgun" to be used (which is not really a shotgun at all, but that's for a different thread), there's no NEED to stabilize it with any other method other than rifling.

As for why do .mils use smooth/fin-stabilized in ordnance delivery, IIRC I believe it's in order to gain a higher velocity (the rifling slows things down a bit), but for non-mil uses, there's no need for that kind of extra velocity, espec. in light of the expense noted above.

Because fin stabilized projectiles dont have the mass that a sabot or rifled slug does. Mass conveys energy to the target. Finned projectiles are meant as high velocity penetrators.

Slugs are for killing animals, not penetrating armor.

Then there's that, too.

rcmodel
November 10, 2009, 03:09 PM
Sabot tank rounds only weigh a fraction of what a standard main gun projectile would weigh.

That allows extremely high velocity of over 5,500 FPS to be achieved at allowable pressure levels.
The high velocity is needed to penetrate armor.

Something you don't need or want in a shotgun used for hunting or SD.

rc

Blakenzy
November 10, 2009, 03:12 PM
Wouldn't it offer a significant improvement accuracywise for smooth bore owners?

Well, I can't find anything on www.sauvestre.com. they only have rifle rounds. Either they don't make it anymore or I have the name wrong.

highorder
November 10, 2009, 03:16 PM
Smooth bore shotguns do just fine for people that hunt with them. Rifled slugs are accurate enough for the range they are intended for.

There's no need, therefore no market for finned projectiles considering the quality stuff available for rifled shotgun barrels. As the good Dr. said, anywhere you are limited to a shotgun for deer, rifled barrels are permitted.

As RC said, even with improved accuracy, you would sacrifice killing power with a much lighter finned projectile.

bigalexe
November 10, 2009, 03:26 PM
I guess the idea of fin stabilized projectiles fired from smooth bores works well enough that it is used in main battle tanks. Why isn't it more popular with shotguns?

I think the difference between a tank gun and a shotgun slug is that with the tank gun if you miss by half a meter it really doesn't matter much because the projectile is still going to explode and at least maim if not kill the intended target. Tank guns have accuracy measured in meters for this reason. A shotgun slug that misses its target by 8 inches will not explode (with few exceptions called bird bombs, but that's another topic entirely) and still have the same effect. When we hunt we intend to kill the target completely so a near-miss is unacceptable.

rcmodel
November 10, 2009, 03:26 PM
I don't think there would be any accuracy improvement.

Forster & Brenneke slugs are inherently stable from the get-go because they are heavy on the front and light on the back like a badminton shuttlecock.

A Sabot gets destabilized to some extent when the sabot seperates.
Then it has to regain stability as it flys to the target and the fins kick in.

When you are talking 20 - 75 yards with a shotgun slug, starting out stable like a shotgun slug has a lot to say for it.

BTW: Sabot anti-tank / tank main gun rounds do not explode.
They are just an inert rod, and drill through enemy armor because they are going faster then a speeding bullet!

rc

Fred Fuller
November 10, 2009, 09:24 PM
http://www.fas.org/man/dod-101/sys/land/m1.htm

http://en.wikipedia.org/wiki/M829

Kinda hard to compare... 120mm vs 12 bore, 5,550 FPS vs. 1600 FPS, thermal sights vs two each Mark 1 eyeballs, computerized gun stabilization system vs. brain, nerves and muscles, etc.

Ever seen an M1A1 doing live fire on the run? Spookiest thing I ever saw, watching that muzzle track as the tank changed inclination and direction.

lpl

Beagle-zebub
November 10, 2009, 09:57 PM
BTW: Sabot anti-tank / tank main gun rounds do not explode.
They are just an inert rod, and drill through enemy armor because they are going faster then a speeding bullet!


Mmmmmm, I don't think that's entirely right. This FAS article says that "DU is a natural pyrophoric material," and that's what those rods are made of. http://www.fas.org/man/dod-101/sys/land/pgu-14.htm

This Global Security article says it is also "self-sharpening." http://www.globalsecurity.org/military/systems/munitions/du.htm

Nasty stuff, that! :evil:

Shawn Dodson
November 10, 2009, 10:09 PM
I tested the Sauvestre fin stabilized slug about 8-9 years ago using a Remington 870P. I still have a few left.

Out of my 870 it was less accurate than a standard foster slug. (My 870 was fitted with a Vang Comp barrel which could have affected accuracy.)

Basically it turned my 12 gauge into a .45-70 Gov't. That's about it.

It had no problem penetrating two pieces of 20 gauge sheet metal set at an angle (simulating a car door), with little deflection.

I tried measuring velocity but one of the sabot halves struck my Oehler 35 skyscreen, damaging two of them.

Intriguing concept.

I also shot 105mm and 120mm sabot projectiles when I was an M1 Abrams tank commander, but I digress.

bigalexe
November 11, 2009, 01:16 AM
Ok I always assumed tank rounds went boom but I guess that's not correct. I do know interestingly that the British Challenger 2 Main Battle Tank uses a rifled 120mm cannon designated the L30A1 which is the only one in NATO.

Thanks for the lesson anyway.

rcmodel
November 11, 2009, 01:57 PM
Some tank rounds do go boom (HEAT), and some don't (KE).

Here is a fairly good description of the different rounds that can be used in the M1 Abrams 120mm smooth-bore cannon.

http://www.fas.org/man/dod-101/sys/land/120.htm

rc

Blakenzy
November 11, 2009, 05:18 PM
Finally found a picture! on a spanish site http://foro.fullaventura.com/viewtopic.php?f=4&t=12182

http://img216.imageshack.us/img216/1948/sauvestreimage19.jpg
http://img216.imageshack.us/img216/7817/sauvestrefrecetg.jpg

rcmodel
November 11, 2009, 05:26 PM
So, lead slug and gold plastic fins.

Same heavy front end - light rear end as the other slugs & stabilized like a badminton shuttlecock.

rc

Shawn Dodson
November 11, 2009, 05:51 PM
Finally found a picture! Yup, that's what I tested.

RandKL
November 11, 2009, 07:03 PM
like a badminton shuttlecock.

*cough* oblique fins *cough* spin stabilized *cough*

;)

r

desidog
November 11, 2009, 07:26 PM
I'm surprised that DRT doesn't have an edition of this load....

rcmodel
November 12, 2009, 02:47 PM
*cough* oblique fins *cough* spin stabilized *cough*Cough all you want to, but the "oblique fins" on a rifled slug do little or nothing to impart spin to the slug.

The super-sonic shock-wave over the nose of the slug leaves them operating in what amounts to an air burble.
There is no laminer air flow over the "rifling" fins to make them do anything much at all.

They are well past 50 yards before they go sub-sonic and even begin to get a little laminar flow over the fins.

The fins are there to give excess lead a place to go when the slug hits a choke and has to squeeze down to get through it. Nothing more.

rc

RandKL
November 12, 2009, 07:31 PM
Cough all you want to

Wow, I've really been taught a lesson there....and it has nothing to do with the entire topic. Then again, I already knew about rifled slugs, too, so maybe I wasn't.

The fins on the FINNED slug in question, RCM, have pretty danged obvious oblique leading and trailing edges that DO impart spin to the FINNED slug in question.

r

rcmodel
November 13, 2009, 12:43 PM
I still contend that there is no laminar air flow over the fins on a super-sonic slug with rifling or fins. The shockwave coming off the nose of the slug leaves a semi-vacuum in its wake until it goes sub-sonic at extended range.

The finned slug may have an airfoil shape, but without laminar air flow over them, they are stalled out, and provide no spin.

rc

highorder
November 13, 2009, 01:07 PM
I still contend that there is no laminar air flow over the fins on a super-sonic slug with rifling or fins. The shockwave coming off the nose of the slug leaves a semi-vacuum in its wake until it goes sub-sonic at extended range.

The finned slug may have an airfoil shape, but without laminar air flow over them, they are stalled out, and provide no spin.


I agree with RC here. Not to mention the moment of inertia provided by the heavy projectile that needs to be overcome by the stubby fins in the slipstream.

The rudder on the Titanic was capable of making turns, but not to the extent necessary. :)

RandKL
November 14, 2009, 12:00 AM
I still contend that there is no laminar air flow over the fins on a super-sonic slug with rifling or fins. The shockwave coming off the nose of the slug leaves a semi-vacuum in its wake until it goes sub-sonic at extended range. The finned slug may have an airfoil shape, but without laminar air flow over them, they are stalled out, and provide no spin.

Contend all you want, RC. The makers of said FIN STABILIZED slug said it does. Who do I believe?

They also advertised that said FIN STABILIZED slug as making 12" groups at 200 yards. Something quite a few users at the time agreed with. In your experience with fin stabilized slugs, do the fins ever stabilize the fin stablized slug inside that range?

Me, I'd guess that since Foster slugs aren't that accurate at 200 yards, the oblique fins are doing a pretty good job of it.

r

Remo-99
November 14, 2009, 10:42 AM
Mmmmmm, I don't think that's entirely right. This FAS article says that "DU is a natural pyrophoric material," and that's what those rods are made of.

U-238/DU penetrators were originally employed for their mass density ratio and lower cost than a tungsten equivelant, the 'pyro' effect was a bonus side-effect.
After penetrating thick bunker walls, the material generates massive heat from friction and will incinerate targets within a certain angle/radius/proximity.
No explosives, just plain old positive temp coeffient of fraction + velocity.

Shawn Dodson
November 15, 2009, 03:36 PM
The fins on the FINNED slug in question, RCM, have pretty danged obvious oblique leading and trailing edges that DO impart spin to the FINNED slug in question. Oblique leading and trailing edges? No. Each fin is tapered on both sides to make them aerodynamic. Their purpose is to facilitate drag stabilization.

-v-
November 15, 2009, 05:55 PM
Erm, so what about the fins on a APDS of the 120mm variety? It seems to me those help stabilize the projectile so it can consistently hit its target.

Although, I agree, it seems that the shock-wave flowing over the nose of the slug would make the fins darn near useless since they would be getting little/no airflow.

Brings up then the whole question of super-sonic aircraft and how they maintain lift and control at Mach 1+?

Remo-99: DU is pyrophoric. When the DU rod impacts, surface layers are sloughed off into dust, the dust will (because of its outer valience shell and the octet rule) spontaneously react with the O2 in the air to form UO2 (uranium Oxide) and a bit of heat.

A similar thing happens when you machine uranium. The shavings have to immediately go into a mineral oil filled bucket or else they will begin to spontaneously combust from contact with the air. The larger and thicker the sample, the less likely the Uranium will combust. Shavings burn easily, slabs not so much.

Think of Uranium like a more reactive magnesium.

Owen
November 15, 2009, 06:01 PM
the difference with the tank gun is that the fins are larger than the body of the projectile, so the correction is constant. With the sub-caliber fins on that slug, it's gonna wobble quite a bit = bad

rcmodel
November 15, 2009, 06:02 PM
My impression is, the 120mm Sabot is very slim and about two foot long, and a jet fighter is way longer then that with an area-rule fuselage design.

I think there is some laminar flow air flow way back where the fins are on those.

On a short-coupled slug, not so much.

rc

RandKL
November 15, 2009, 10:36 PM
Oblique leading and trailing edges? No. Each fin is tapered on both sides to make them aerodynamic.

Wrong. They're sliced on the fronts on ONE side and on the backs on the opposite side to provide spin as the manufacturer stated when those were hot on the market several years back. If you look a bit, you'll probably find the original ads on the web somewhere. Heck, you can look at the pics above and see that.

rich

mlkAvEAT
February 21, 2010, 03:44 PM
Sorry for bringing an old post back to life but I just found it and I wanted to give my input and correct a few things. My intent isn't to single out rcmodel, just to fix some statements.

Cough all you want to, but the "oblique fins" on a rifled slug do little or nothing to impart spin to the slug.

The super-sonic shock-wave over the nose of the slug leaves them operating in what amounts to an air burble.
There is no laminer air flow over the "rifling" fins to make them do anything much at all.

They are well past 50 yards before they go sub-sonic and even begin to get a little laminar flow over the fins.

The shock wave over the front of this projectile would be an oblique shock wave which would indeed leave the entire projectile in a "bubble", but not a low pressure bubble. In contrast the pressure after the shock wave would be much much higher than the pressure of the air in front of it.

I still contend that there is no laminar air flow over the fins on a super-sonic slug with rifling or fins. The shockwave coming off the nose of the slug leaves a semi-vacuum in its wake until it goes sub-sonic at extended range.

The finned slug may have an airfoil shape, but without laminar air flow over them, they are stalled out, and provide no spin.

You are very correct, there is absolutely no laminar flow over the projectile, or hardly any object traveling past Mach 1. Laminar flow is very hard to accomplish even in subsonic conditions, I would venture to say that even high performance sailplanes struggle to keep the flow of air laminar over the entire chord of a wing. (Little things like a break between pieces of skin on a wing or a bug splat are enough to stop air from being laminar.)

The bit mentioned about the semi vacuum is entirely wrong. Like I stated before, the air pressure increases many times so the air around the projectile would be much thicker. The air does however slow down a lot, so while air pressure around the projectile is much higher the air velocity is much lower.

I can't comment too well on the part about the fins being stalled out, though I really doubt it.


Erm, so what about the fins on a APDS of the 120mm variety? It seems to me those help stabilize the projectile so it can consistently hit its target.

Although, I agree, it seems that the shock-wave flowing over the nose of the slug would make the fins darn near useless since they would be getting little/no airflow.

Brings up then the whole question of super-sonic aircraft and how they maintain lift and control at Mach 1+?

We could have a long talk about that ;) But you should be able to get the gist from the above. At Mach 1+ air around the plane slows down, pressure goes up, just makes a new set of design criteria.

My impression is, the 120mm Sabot is very slim and about two foot long, and a jet fighter is way longer then that with an area-rule fuselage design.

I think there is some laminar flow air flow way back where the fins are on those.

On a short-coupled slug, not so much.

There is probably no laminar flow on the 120 mm projectile, even if the fins are far enough out from the body to escape the shock cone created at the nose the leading edge of the fins would make their own shock waves. I won't say its impossible to have laminar flow past Mach 1.

These fins would indeed do something, but if that something is enough to make the round effective I don't know.

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