The Sling: king of the missile weapons

[Patrick Waterson]

FWIW it is generally reckoned that 80J (don't ask me what that is in foot-pounds) is enough to kill a man from blunt force trauma.  (No idea what the equivalent figure is for an elk.)  Most longbow arrows shot with around 150lb pull can achieve this up to 200yds.  The weight of reconstructed longbow arrows varies from 1270 grains for short bodkins up to 1925 grains for a quarrel-type bodkin.

1 foot pound is equivalent to1.3558179483314 joules

Conversely, 1 joule = 0.737562149277 foot pounds

Hence 80 joules equates to 59 foot pounds - so a 'blunt force trauma instrument' should deliver at least 60 ft lbs (or 81.35 joules) at impact - more if the opponent happens to be a Philistine with Anakim heritage. 

[Nick Harbud]

This figure is taken from the technical appendix to Great Warbow and, I think, does have some problems (for me anyway).  The actual quote is :

It is usually considered that a penetrative impact delivering 80J of energy on an unprotected person is likely to be lethal (clearly the the part of the body hit will affect the outcome to some extent)

The figure is actually related to a penetrative injury, and it depends on where the target is hit.  The figure is oft quoted as the force of an arrow hitting will be lethal regardless (blunt force trauma) but maybe it is more the force needed to actually penetrate deeply enough to do serious damage?

There is probably more to be done on blunt force trauma and armour i.e. the effect of a non-penetrating or slightly penetrating blow on the insides of a human.  As modern soldiers wear armour again, I wouldn't be surprised if there are studies and methodologies out there.

Other people quote this - Secrets of the English Longbow uses it as do any number of TV documentaries.  Wikipedia has an entry for those interested in this gruesome subject http://en.wikipedia.org/wiki/Blunt_force_trauma.  Also this fascinating article on modern protection. http://en.wikipedia.org/wiki/Ballistic_vest  Incidentally, I agree with Tony that most people using the 80J figure tend to ignore the effect of body protection.

[Patrick Waterson]

An important part of modern (ballistics-related) calculation of the force necessary to wound or kill is the hydrostatic shock aspect.  Hydrostatic shock creates secondary disruption to tissues and internal organs by pressure wave action and fluid displacement (hence 'hydro-static').  One may note that the figure of 300 foot-pounds (410 joules) is regarded as the effective minimum to produce disabling effects and 500 foot pounds (680 joules) is recommended to be reasonably sure.

Slow-moving torsion-propelled rounds (arrows, slingshot) tend not to have hydrostatic shock effect as it depends upon propagation of waves of a certain frequency and energy level.  Slow-moving gunpowder rounds (from pre-1800 black powder weapons) also tended to rely on direct impact rather than secondary effects for a kill.  Such rounds were much heavier than their modern counterparts for this reason (sling bullets and musket balls seemed to coalesce weight-wise around the ounce).

I suspect the figure of 80 joules (59 foot pounds) may be more along the lines of the minimum force required to get a missile from initial skin penetration into an artery or internal organ - anything less and it will perhaps stop part-way.

[Nick Harbud]

I suspect the figure of 80 joules (59 foot pounds) may be more along the lines of the minimum force required to get a missile from initial skin penetration into an artery or internal organ - anything less and it will perhaps stop part-way.

I would sure about 80J being so puny.  I mean, it is the equivalent of 1kg dropped from 8m, which is quite enough to kill someone or at least seriously incapacitate them.  However, as Tony points out, it needs to hit the right spot.

[Erpingham]

The issue I have with the 80J thing is how it is sort of a mantra.  As Nick says, a quick thought experiment shows that a 1kg rock falling from 8m could kill you if it fell on your head.  If it fell on your foot it would probably disable you.  So it isn't the shock of a certain force hitting you that causes death, it what happens to your body on impact.  Also, arrows tend to cause sharp force not blunt force trauma.  Blunt force trauma from arrows is more likely to be an issue if the target has armour on, and that is no easy calculation (it is essentially about what happens to the energy - how much goes into breaking the armour, how quickly the arrow strike energy is absorbed (elasticity/plasticity), over how wide an area the point impact energy of the arrow is spread/diffused by the armour).

But to return to the sling for a moment, we are much more dealing with blunt force trauma.  There are some fun things to be said about big slingshots versus sling bullets (KE is a square function of speed, so smaller bullets could do more more damage if they travelled significantly faster, the impact area of a small bullet may be more efficient at transfering blunt force etc.).

It is an interesting question whether we should maintain this discussion of weapon trauma and ballistics here or split out - what do folks think?

[Patrick Waterson]

If it grows, specifically beyond the effectiveness of slings, we split it.  If it subsides, or remains sling-oriented, we keep it here.

Lacking the refinements of modern physics, classical military thinkers settled for looking at effects (which they were in a better position to do than we are) and seem to have decided that slings were more effective than other missile types against armour, having noticed that non-penetrating sling wounds nevertheless occasionally (or perhaps often) put a man down.

I understand that Balearic slingers used small stones for long range shots, lead bullets for medium range shots and large stones for close range shots (and had a different sling for each range, wrapping those not in use about their waist and head).  Incas seem to have been satisfied with small stones for general use (then again, until the Spanish arrived, metal-armoured opponents were not a fact of life).  On this basis we might presume that small stones have the best travelling capability and enough force when arriving at the end of a long flight to cause harm, while lead bullets do more (and/or better, from the shooter's point of view) damage in their optimum range bracket, but nothing beats a good, big stone for sheer knockdown capability.

The next question would be: can we validate (or challenge) these presumptions?  And how do they fit with blunt force trauma energy considerations?  (One might note in passing that sling bullets seem to have had good penetration against unarmoured opponents.)

[Nick Harbud]

But to return to the sling for a moment, we are much more dealing with blunt force trauma.  There are some fun things to be said about big slingshots versus sling bullets (KE is a square function of speed, so smaller bullets could do more more damage if they travelled significantly faster, the impact area of a small bullet may be more efficient at transfering blunt force etc.).

FWIW, when I was looking at trebuchet and early bombard ballistics a few years ago it was fairly obvious that although medieval artillerists did not have the understanding of Newton, they were aware that increasing either projectile speed or mass could increase the effect on the target.  With trebuchets and other mechanically propelled weapons, the energy that can be imparted is limited by the counterweight, stretched sinews or whatever else one uses and there is a fairly low limit to the velocity that can be achieved, no matter how light one makes the projectile - typically somewhere in region of 60-100m/s.  Therefore the only way to increase the punch was to increase projectile mass.  There was also a limit to how large one could make the projectile, based on the strength of the catapult construction materials and the ability of the crew to manhandle the ammunition - around 150kg.

Early gunpowder changed this only somewhat.  Partly this was because the early gunpowder did not burn as well as later preparations and partly it was due to the early gun founders inability to cast cannon that would withstand high pressure.  Again, the artillerists resorted to low velocity, high mass bombardments.  Somewhere around the middle of the 15th century gunpowder mixtures, gun manufacture and experimentation all caught up with each other and gunners realised they could achieve the desired effect with smaller cannon balls shot at a higher velocity.

Incidentally, the force exerted by an impact is equal to the rate of change of momentum (m*v/t).  The stress exerted is equal to the force divided by the area.  Projectile area increases in accordance with the diameter squared, whereas the mass increases according to diameter cubed.

[Chuck the Grey]

I have an article from Scientific American on the sling as a weapon. If I remember correctly, the article if from the late seventy's. I haven't read it in years and had forgotten about it until this discussion started up. The file is to large to attach to this post, but if anyone is interested, I will be glad to e-mail it to you.

[Nick Harbud]

I have an article from Scientific American on the sling as a weapon. If I remember correctly, the article if from the late seventy's. I haven't read it in years and had forgotten about it until this discussion started up. The file is to large to attach to this post, but if anyone is interested, I will be glad to e-mail it to you.

Unless you have checked the position with respect to the magazine's or the author's copyright it is probably as well not to reproduce it on a forum like this.  The 1970's is a bit early for such publication's on-line archives, but you never know.  Have you tried contacting Scientific American to see what the score is? 

Failing that, is it possible for you to summarize the article here?

[aligern]

chuck, you can happily quote chunks for the purposes of research and review.
Most interesting to see the conclusions.
Roy

[Erpingham]

I'd guess from a quick google that the article in question is Korfmann's from 1973.  I wasn't able to find that online but did find this which might be of interest :

http://www.academia.edu/176644/New_Experimental_Data_on_the_Distance_of_Sling_Projectiles

[Andreas Johansson]

Possibly of interest wrt kinetic energy: Bert S. Hall's Weapons and Warfare in Renaissance Europe (p145) describes a test in which a early modern pistol was fired at a 16C breastplate from 8.5 m range. The calculated impact energy was 907 J (so more than eleven times the supposed "blunt force trauma" lethality threshold). The bullet did penetrate the breastplate, but in doing so expended practically all it's energy, failing to penetrate the linen beneath. The investigators concluded that a man wearing the breastplace would not have been killed or seriously injured, but merely bruised.

The original citation is:
Kalaus, P. "Schießversuche mit historischen Feuerwaffen des Landeszeughauses Graz und der Prüf-  und Versuchsstelle für Waffen und Munitionen des Amtes für Wehrtechnik." In Von alten Handfeuerwaffen: Entwicklung, Technik, Leistung ed. Peter Krenn, 41-113. Veröffentlichungen des Landeszeughauses Graz, 12. Graz: Landesmuseum Johanneum, 1989.

[Chuck the Grey]

Mea culpa. I didn't even think about copyright and I know better. It appears that old timers disease is worse than I thought.

I'd guess from a quick google that the article in question is Korfmann's from 1973. 

Yes it is Korfmann's article. It's older than I thought.

I'll read the article and post a summary here in the next couple of days. I'm still recovering from Thanksgiving; clean up, food coma, etc.

[Dave Beatty]

Possibly of interest wrt kinetic energy: Bert S. Hall's Weapons and Warfare in Renaissance Europe (p145) describes a test in which a early modern pistol was fired at a 16C breastplate from 8.5 m range. The calculated impact energy was 907 J (so more than eleven times the supposed "blunt force trauma" lethality threshold). The bullet did penetrate the breastplate, but in doing so expended practically all it's energy, failing to penetrate the linen beneath. The investigators concluded that a man wearing the breastplace would not have been killed or seriously injured, but merely bruised.

I would agree with investigators on this one.  I can say from personal experience that being shot with an AK-47 at long range (1000 yards or so) the bullet did not penetrate my old Vietnam issue flak jacket but it sure did knock me on my ass and leave a nasty bruise over most of my chest.  In a different engagement, a colleague was shot in the head at close range (20 yards) by an AK-47 and the bullet did not penetrate his new fangled Kevlar helmet (this was in Grenada in 1983).  The kid's helmet went flying but he was entirely uninjured. The helmet (complete with 7.62 bullet lodged therein) is in the museum at Ft Bragg last I saw it.

[Patrick Waterson]

I would agree with investigators on this one.  I can say from personal experience that being shot with an AK-47 at long range (1000 yards or so) the bullet did not penetrate my old Vietnam issue flak jacket but it sure did knock me on my ass and leave a nasty bruise over most of my chest.

Dave, I am surprised anyone could hit a target with an AK47 at 1,000 yards or so.  Are you sure it was not a Dragunov (SVD-63) sniper rifle?  Those things were pretty accurate and I suspect that Charlie was aiming for your head but thankfully failed to allow for bullet drop.

Muzzle velocity on an SVD is about 830 m/s compared with the AK-47's 715 m/s, this being from a 7.62x54mm cartridge instead of 7.62x39mm.  Not sure what the impact energy would be at 1,000 yards but the word 'considerable' comes to mind.

I'd guess from a quick google that the article in question is Korfmann's from 1973.  I wasn't able to find that online but did find this which might be of interest :

http://www.academia.edu/176644/New_Experimental_Data_on_the_Distance_of_Sling_Projectiles

Yes, of particular interest is this snippet from the conclusion:

"The previous maximum downslope distance model very significantly underestimates the range that an experienced adult male slinger can cast stones."