Flechettes, and Extreme Velocity Rounds

W

wildkard

New member
Has there been any research done on the effects of flechettes, or extremely high velocity low mass rounds.

What are your thoughts on the idea of a 3mm 20gr. round traveling at 10,000 ft/s?

Would it just punch a tiny hole in the BG or would it cause massive trauma through tempoary cavitation?

Also what would the recoil be like, and how fast would the velocity drop off with range?

Any comments would be greatly appreciated. Thanks.
 
Flechettes are not for one-on-one close in defense or offense. Flechettes are best used when fighting a large force with a smaller one. By getting one guy with a load of flechettes, two others are tied up carrying him because his pain is terrible, and they don't carry x-ray machines out to the battlezone. That's three guys down with only one shot.

As for the rest of it:

What are your thoughts on the idea of a 3mm 20gr. round traveling at 10,000 ft/s?

I'm wiondering the type of material that could handle that type of centrifugal force and still open up on impact. I'm not sure if there is one right now. I think that a projectile that small going that fast would have to be solid...what would it do on impact? Probably sail right through with no slow-down. I'd almost bet that the heat fromthe round would even sear the flesh on the target and there would be minor bleeding if any. I don't "think" there would be a hydrostatic effect, just because the projectile would go so fast and upset the tissue so little.

Would it just punch a tiny hole in the BG or would it cause massive trauma through tempoary cavitation?

Also what would the recoil be like,

Very light, I'll bet.


and how fast would the velocity drop off with range?

FAST.

Any comments would be greatly appreciated. Thanks.
 
Flechettes have been used on and off, AFAIK, since WW I, when darts were dropped from airplanes.

They were used in "beehive" rounds in 'NAM. The problem with using flechettes- in the sense of an extremely small dart, not a huge penetrator like the discarding sabot anti-tank rounds- is that a single flechette causes little damage. It's just a tiny little arrow, zip! Right through.

As Steve Smith pointed out, velocity from extremely lightweight projectiles drops off very fast. So, with current technology, even if you COULD get, say 8,000 fps, you would have something that would use quite a bit of energy, would do little damage, and would only be effective at close range.

Until lightweight rail gun technology is perfected, hypervelocity rounds will be impractical. Part of this is due to the effects of the heat from very high velocity (gunpowder) rounds. This has been a problem ever since the Lee Naval rifle of 1895, which had the astonishingly high velocity of 2,460 feet per second! :D These rifles reportedly had very short barrel life, compared to other service rifles of the time.

The rail gun, in contrast, works by using electricity to gradually speed up a lightweight projectile.
 
Two candidates in the Army's Advanced Combat Rifle program (late 1980's), produced by Steyr-Mannlicher and AAI, fired a 1.5mm diameter, 41mm long, 10gr steel flechette at a velocity of over 4500fps.

These flechettes would do one of two things: 1) they would either pass completely through a target, point forward, producing very little disruption, or 2) they would fishhook and produce a little more disruption than the ones that passed through point forward.
 
A book you should check out...

Yes, the US Army did quite a lot of research on flechettes between Korea and Vietnam, and a lot of this material is covered in the book "SPIW: The Deadliest Weapon That Never Was", by Stevens & Ezell. These things had fantastic velocity and penetrating power, but accuracy was so poor they ended up just pouring them downrange to try to get an acceptable hit probability. When they DID hit, they ended up buckling in half and turning into "fish hooks", and would've been a real mess for a surgeon to deal with (the book shows some x-rays of tests they did on swine with these things). In the photo below, the most common flechette encountered is the XM144, third from the right. These were manufactured by IVI in Canada at a cost of $3.50 US PER ROUND, and were fired at a cyclic rate of 2,000 rounds per minute.
View


[Edited by SDC on 05-17-2001 at 01:10 PM]
 
I love math.

If we make some simplifying assumptions like pressure and acceleration are constant while the bullet is in the barrel, we can figure out how forces and pressures will scale.

Take a 5.56mm 62gr projectile (0.00402kg), leaving a 20" (0.5m) barrel at 3000 fps (914 m/s). Its acceleration within the barrel is 835,000 m/s^2, or 85,000 "g's". The area is A = pi*(cal/2)^2 = 2.43e-5 m^2. The average pressure is p = m*a/A = 138e6 n/m^2.

Now take a 3mm 20gr (0.0013 kg) bullet, leaving a 20" (0.5m) barrel at 8,000 fps (2438 m/s). Its acceleration within the barrel is 5,944,000 m/s^2, or 607,000 "g's". The area is A= pi*(cal/2)^2 = 7.07e-6 m^s. The average pressure is p=m*a/A = 1093e6 n/m^2.

Note that the linear acceleration of the 20gr projectile is about 7x the acc. of the 5.56 projectile. Also, the action, barrel, and "brass" (if it exists) for the 30gr projectile will have to withstand almost 8x the pressure of the 5.56 round.

I interpret this to mean that there is a point of diminishing returns when you consider the entire package that will shoot these projectiles.

-z

[Edited by smithz on 05-17-2001 at 03:37 PM]
 
Thanks, SmithZ. I was hoping someone could show this mathematically. Much obliged.

------------------
This is no head trip, honey.
This is a collision on the road...
 
If you want to do do approximations of how average pressure scales with mass and velocity, you can use this:

p = m * V^2 / (A*2d)

where m is mass, V is muzzle velocity, A is pi*(caliber/2)^2, and d is the barrel length.

Solving this for V yields

V = sqrt( p*A*2d/m ), or that possible velocity scales with the sqrt of the ratio of A/m, or caliber^2 / m.

The ratio of this quantity for 5.56(62gr) :: 3mm(20gr) is 1.05 :: 1. In other words, the you can attain about 5% more velocity with this 5.56 round than that 3mm round, for the same barrel length and average pressure.

This is all based on the simplifying assumptions I stated earlier, not to mention physical constraints like, does an appropriate powder exist?

-z

ps. Interestingly, if I compute V for a .308, 150gr projectile, using the same pressure computed for 5.56 (138 MPa), I get 2709 FPS, which is a good sanity check.
 
Flechette are lethal but have no stopping/knock-down power, what kills is bleeding out from the many needle-like wounds. Not always the best option. Bullets are more effective and buckshot more so for stop kills.
 
High velocity accupuncture

The army did many tests in the '50s-'60s with the SPIW (Special Purpose Individual Weapon)project and in the late '80s with the now defunct (thank god) ACR project (Advanced Combat Rifle).
The end result being multi-millions (at least 40) wasted and at least 4 prototypes that were until recently in my units' arms room until donated to the Infantry Museum at Fort Benning Ga.
Tech data that I have is as follows:
1: Colts' candidate: a highly modified M-16 look alike that fired duplex ammo (two bullets in tandem) of (F) 35gn and (B) 33gn. Velo about 2900fps max rng. about 300M.
2: AAI Corp candidate: fired a 10.2gn flechette at about 4650fps from a 5.56mm case.
3: Steyrs' candidate: Looks quite a bit like an AUG with a case design all its' own. w/flechette at 9.85gn at 4900fps.
4 H&Ks' cadidate: was the G-11 w/no real changes to it's configuration.
Ballistically singularly flechettes are unimpressive but as an area weapon from a 105mm howitzer or larger it is not to be good inside of its' burst radius-A 105 contains about 6000 flechettes.
 
Thanks guys!

Sorry for not replying sooner I was out on manuevers with ROTC.
I guess the extremely high velocity rounds will have to wait for pocket sized railgun technology, which will have to wait for pocket sized nuclear reactors.

Anyway I was reading a Military Sci-Fi novel, and the primary weapon was a submachinegun railgun which fired either metal coated glass bullets, or tungsten penetrators. The glass bullets were for use against unarmored targets, and would shatter on impact, while the tungsten penetrator rounds were for armored personnel, or equipment.

Anyway back to reality, how about something in between the 5.56 NATO, and the 7.62 NATO rounds, I've heard good things about 6mm.
 
Resurrecting an old thread.

Here's an answer to the question, "How fast will velocity bleed off?"

I used an approximate BC based on the existing 0.17 caliber bullets. 3mm would be about 0.118 caliber.

Code: 
 _BC_ _MV_         0     200     400     600 | YARDS
0.120 8000 >   -1.48   -0.00   -4.80  -27.74 | > 3mm "wildkard", 20gr
                7979    4917    2925    1591 | fps, velocity

0.120 4000 >   -1.46   -0.01  -28.37 -152.90 | > 0.17 MACH IV, 20gr
                3989    2322    1219     854 | fps, velocity

0.255 3200 >   -1.45   -0.01  -22.12  -86.68 | > .223, M193
                3196    2467    1845    1347 | fps, velocity

0.400 2700 >   -1.43   -0.01  -25.97  -91.97 | > .308 surplus
                2698    2268    1880    1538 | fps, velocity

G1 drag model.
 
The G11 did NOT fire fletchettes. It fired a small bullet, yes, but it was a bullet and not a little dartlike penetrator.
HK as far as I know, has not made a fletchette weapon. Steyr has... and its the goofiest thing I have ever seen next to a Birdman system.
 
Yeah, not bad coming out of a 120MM smooth bore.

These Fletchettes are best fired out of a smooth bore gun. This gives added velocity. Also Fletchettes work best in large numbers. For example, the 12 gauge loads you can find. In Idaho, a long time ago before TFL, I used Fletchette loads out of an Bennelli to bust crows. Did a wonderful job of it too. A direct hit would just about explode those birds. And at a good range too.
A single dart out of a rifle would not give you much advantage in anything. Out of a smooth bore gun, say an unrifled M16, you will get a greater velocity advantage... Range estimation is no longer important since you are firing with a very flat trajectory. However the terminal ballistics will be laughable and the rounds ability to buck wind will be pathetic. A crosswind will throw off you shot so badly as to make the attempt no better than Woody Allen's chance to kick a 40 yard field goal.

Being able to judge ranges is a dying art. I have to admit I am no longer very good at it. But there are tools you can use that will measure distances for you. It takes just a moment to adjust your BDC for the range, and then you can drop a nice fat heavy slug into your target that will do its job as advertised.

I can't see a fletchettes real application in the military... Not assault rifles, or snipers... Cannons, shotguns and the like are fine... MAYBE out of machineguns. Like a fast firing machinegun build on the M2 action that will let you fire a subcaliber penetrator that has some momentum behind it.
 
Fletchetes, I had heard, had a real nice air to air application for helicopters and other slow flying aircraft. I believe they took a FFAR rocket (the type commonly used on AH-64's), and loaded the tip with someting like 1200 fletchetes. When the thing detonated, the fletchetes spread out, creating something of a birdshot pattern spread over several hundred square meters at super sonic speeds. This would cause problems for any jet aircraft passing through the circle of fletchetes.

SDC,
What are the cartridges in the webpage you linked to?
I'm guessing 9mm THV, 9mm, .45ACP, 7.62x39, 7.62x51, .30-06, .30-06, Fletechete, ??, .50BMG?
 
Cool sectional view...

Foxy, SDC, let me guess...
9x19 THV, 9x19 with homogeneous brass bullet, 45 ACP with mild steel bullet, 22 SCAMP with 40gr. steel-lead bullet, 5.45x40 (steel cased) with the mild steel+lead filler+air space bullet, 5.56x45 with 55 FMJ (M193), 5.56x45 SS109 load, XM 645 5.6x52.8 flechette, 7.62x54R with ? bullet, 30-06 hard steel core AP 172gr.
 
Close; left to right, these are: 9mm THV, 9mm KTW, 45 ACP National Metals AP, a 5.7mm P90 AP round, a 5.45 x 39mm Soviet round, a 55 grain M193 5.56 NATO round, an SS109 64 grain semi-AP round, an XM164 SPIW flechette round, a .303 Britsh Mk VII ball round, and a US M2 AP .30-06 round.
 
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