# Are foot pounds of energy (fpe) a poor indicator of lethality?



## Konrad (May 2, 2020)

Hello fellow slingshot shooters,

I have a question and would like to open the subject up to discussion. Are Foot Pounds of Energy a poor measurement of lethality.

I did the calculation of a cricket ball (163grams) 2515.47 grains traveling at 47m/s (154.3fps) 161km/h produces *132.5 foot-pounds*

A 8mm ball bearing (2.09grams) 32.25 grains traveling at 118m/s (387.1fps) 424.8km/h produces *10.73 foot-pounds*.

The cricket ball produces 12.3 times more foot pounds of energy than the 8mm steel but it would be rediculous to try and hunt with a cricket ball.

Are foot pounds of energy a poor indicator of lethality? According to these figures they are. Is ballistics gelatine a more accurate measurment?

Your thoughtful contributions to this question are very welcome.

PyramydAir Airgun Calculator
https://www.pyramydair.com/widgets/convert.php?Units&u=14

Salutations to all. Paul.


----------



## Konrad (May 2, 2020)

Thank you wll,

Blunt trauma? the Taylor Knock Out formula

https://slingshotforum.com/topic/39656-blunt-trauma/?p=488386

Taylor Knock Out formula: Quote

"Unlike foot lbs of energy, M x V squared/450250 Momentum is a function of pure mass x velocity.

A 22lr has about 128fpe but 48,000 units of momentum

A 120gr lead ball at 200fps has only 10.6fpe but has 24,000 units of momentum ... half of what a 22lr does

The blunt trauma of a slingshot is pretty impressive

If you use the Taylor Knock Out formula the slingshot is even more impressive, with a slingshot it is about the smash

22lr ......... 40gr x 1200v x .224dia = 10752/7000 = 1.538 Taylor

slingshot ......... 129gr x 200v x .385dia = 9240/7000 = 1.32 Taylor

Taylor factor was used for an non scientific unit to measure the effect of bullets on game, showing that big heavy projectiles are very effective on game animals. Taylor devised this formula after hunting and seeing thousands of animals being shot by a variety of calibers and seeing the effects of heavy slower moving projectiles on game. It pretty much has stood the test of time in real life situations.

wll"

8mm steel = 32.25gr x 387v x .314 = 3,918/7000 = 0.559 Taylor

PK


----------



## Henry the Hermit (Jun 2, 2010)

FPE is a generally accepted indicator of lethality for all projectile weapons. Other factors include penetration and energy transfer. Hunting arrows depend on penetration,hunting bullets on energy transfer plus penetration. Slingshot are more of a blunt force tool, so IMO, large lead balls at 200+ fps are the most lethal slingshot ammo.


----------



## BushpotChef (Oct 7, 2017)

Paul.Konrad said:


> Thank you wll,
> 
> Blunt trauma? the Taylor Knock Out formula
> https://slingshotforum.com/topic/39656-blunt-trauma/?p=488386
> ...


I had no idea about this formula but it really vindicates a feeling I've had for some time now which is the diameter of the load is an inherent characteristic of how a slingshot kills. A .36 cal 65 gr. lead ball simply doesn't transfer energy like a 5/8" glass marble of similar weight. The BFT being the primary killer, FPE can be a confusing way of looking at things.

Sent from my LM-X210APM using Tapatalk


----------



## Griffo (May 22, 2020)

It's a flawed comparison from the outset because no one hunts with cricket balls. Should stop there.

For the types of projectiles which are used for hunting, joules of energy imparted will be proportional to lethality. Don't think this requires further examination.

Stuart Broad and Jimmy Anderson are lethal with the cricket ball. Don't know if either has a slingshot but I'm betting both would be a good shot with one. :thumbsup:


----------



## Konrad (May 2, 2020)

Please all contribute your thoughts. I would like to hear what is the most accurate way to measure a slingshots power. fpe, momentum, Taylor factor, ballistics gel. stopping power, ballistics pendulum, there are a plethora of ways to measure the power of the slingshot. and I am interested in every one's thoughts on this.

I would like to thank you all for your contributions so far..

I my self am leaning towards ballistics gel and a chick carcass but please share your thoughts.


----------



## BushpotChef (Oct 7, 2017)

I guess I didn't add how I measure the juice my setup has: some folks opt for the bean can test, I prefer a full soda can. Most grocery stores have a basket of dented single sodas that's where I grab mine, usually tonic water. Give it a gentle shake to pressurize the can, back off to your average hunting distance, for me this is around 40 ft. Send your shot and if you either get a pass through or really open the can up, aim for the head and head for the woods. 

Sent from my LM-X210APM using Tapatalk


----------



## Griffo (May 22, 2020)

For measuring the exit energy of whatever you happen to be shooting, a chronograph and some maths. I.e. the energy of the projectile shortly after leaving the pouch.

For seeing how different ammo impacts small species shooting a chicken carcass I think would give the best (reliable) results.

My missus would give me the cold shoulder if I put the Sunday roast in the catchbox. Warnings are possibly advised.

I think ballistics gel is meant to mimic the density of human flesh. But still a consistent medium to experiment with if you can find some.


----------



## robbo (Jun 8, 2019)

Griffo said:


> It's a flawed comparison from the outset because no one hunts with cricket balls. Should stop there.
> 
> For the types of projectiles which are used for hunting, joules of energy imparted will be proportional to lethality. Don't think this requires further examination.
> 
> Stuart Broad and Jimmy Anderson are lethal with the cricket ball. Don't know if either has a slingshot but I'm betting both would be a good shot with one. :thumbsup:


hey griffo a 1974 to 76 jeff thomson bowling full toses would probably take out a deer. wouldnt want to be in a fox hole thinking hes to far away to through that grenade.all good fun mate lol.


----------



## robbo (Jun 8, 2019)

BushpotChef said:


> I guess I didn't add how I measure the juice my setup has: some folks opt for the bean can test, I prefer a full soda can. Most grocery stores have a basket of dented single sodas that's where I grab mine, usually tonic water. Give it a gentle shake to pressurize the can, back off to your average hunting distance, for me this is around 40 ft. Send your shot and if you either get a pass through or really open the can up, aim for the head and head for the woods.
> 
> Sent from my LM-X210APM using Tapatalk


hey Bushpotchef,glad to hear your yousing soda and not that wonderfull amber fluid we call beer shooting a tin of beer down under could get you arrested mate or worse lol.


----------



## BushpotChef (Oct 7, 2017)

robbo said:


> BushpotChef said:
> 
> 
> > I guess I didn't add how I measure the juice my setup has: some folks opt for the bean can test, I prefer a full soda can. Most grocery stores have a basket of dented single sodas that's where I grab mine, usually tonic water. Give it a gentle shake to pressurize the can, back off to your average hunting distance, for me this is around 40 ft. Send your shot and if you either get a pass through or really open the can up, aim for the head and head for the woods.
> ...


Hahaha never my friend this is Canada...

We would NEVER condone such alcohol abuse!!  

Sent from my LM-X210APM using Tapatalk


----------



## Henry the Hermit (Jun 2, 2010)

Many slingers can't afford, or don't want to invest, in a chrony. IMO, a valid test of whether a slingshot/ammo combo is powerful enough for small game is to suspend a steel vegetable can on a string, so it swings free. If you can penetrate (make a hole) in the can, you can kill a rabbit or squirrel with it.


----------



## robbo (Jun 8, 2019)

Henry the Hermit said:


> Many slingers can't afford, or don't want to invest, in a chrony. IMO, a valid test of whether a slingshot/ammo combo is powerful enough for small game is to suspend a steel vegetable can on a string, so it swings free. If you can penetrate (make a hole) in the can, you can kill a rabbit or squirrel with it.


hey henry is the can empty or full of water and just one side or two mate


----------



## vince4242 (Jan 11, 2016)

Yes Henry inquiring minds need to know?


----------



## Konrad (May 2, 2020)

Thank you Henry and BushpotChef,

Here is a blog discussing the tin can method as a means to measure Blunt force trauma. .

Warning some dead animals (rabbits and pigeons):

*The Slingshot as a Projectile weapon*

http://nicos-resorterablog.blogspot.com/2012/07/the-slingshot-as-projectile-weapon.html

I am worried my slingshot rifle might not have sufficient power to be used on a rabbit (8mm steel), I would like to be as humane as possible. According to Chair gun pro at 25 yards I will still be producing 7.5fpe 323.9fps. This has lead me to ask this question.

Very interesting, I thoroughly enjoyed your inputs into this discussion.


----------



## wll (Oct 4, 2014)

:- )

For slingshots and the heavy ammo I was using back in the day, I used the simple formula of M x V = um.

The Taylor formula is much better and it really shows what that "TOY" slingshot can really do. Yes units of energy are a nice figure, but it is the momentum that really counts.

Nice post, I completely forgot about the Taylor formula.

wll


----------



## Konrad (May 2, 2020)

Griffo there are many recipes of ballistics gel on youtube.

Here is Joerg Sprave touring a gelatin factory and discussing the U.S.A and German versions of it and part of the process.

*The Ballistic Gelatin Myth Explained*






Here is a example of a recipe on Youtube

*How to make ballistic gel-The right way step by step*






Here is Game Keeper John shooting a raw Chicken carcass

*GAMEKEEPER CATAPULTS POWER & IMPACT TEST ON A RAW CHICKEN & CHRONY TESY*






I think over time I might try a few of the mentioned methods, tin can, ballistics gel, raw chicken and finally a rabbit over time. There are other videos of Game Keeper John shooting a dried out pigs skull and Joerg Sprave shooting a bit of pork and skin.

Excellent discussion, if anyone else wishes to contribute to the discussion please do. Constructive and thoughtful comments are most welcome.

Salutations PK


----------



## wll (Oct 4, 2014)

Paul, this is a great thread. back in the day i was very much into "POWER" and I was tossing ammo in the 125-314 gr range, It was not the fastest, but it had so much momentum it could knock down a house. Yes you can get a lot of energy by chucking a light projectile fast, but the real killing power from a slingshot is a heavy object flying at a respectable speed.

wll


----------



## Henry the Hermit (Jun 2, 2010)

robbo said:


> Henry the Hermit said:
> 
> 
> > Many slingers can't afford, or don't want to invest, in a chrony. IMO, a valid test of whether a slingshot/ammo combo is powerful enough for small game is to suspend a steel vegetable can on a string, so it swings free. If you can penetrate (make a hole) in the can, you can kill a rabbit or squirrel with it.
> ...


Empty, free swinging can, full penetration of at least one side. Unfortunately, I didn't make a video of that test, but here's one of the can full of water, sitting on a board.


----------



## Konrad (May 2, 2020)

Thank's for contributing Henry, awesome a pass thru.


----------

