A Letter From Russ Guthrie
by Russ Guthrie
7/18/2006
Editor's Note: The following article was written by Russ Guthrie and posted on the Atlatl Community site It includes an article written by Daryl Hrdlicka of the Jeffers Petroglyphs Historic Site.
To the PA Game Commission:
From your April 2006 meeting...
MR. POUSS: Mr. President, the next item on the agenda is on page 15. It relates to adoption of proposed amendments to §§131.2 and 141.41 of Title 58.
To effectively manage the wildlife resources of this Commonwealth, the Game Commission, at its January 24, 2006 meeting, proposed the following changes:
Amend §§131.2 and 141.41 (relating to definitions and general) to define and implement the use of the atlatl and dart during any firearms deer season.
PRESIDENT BOOP: Referral to the Law Enforcement Committee.
MR. SCHLEIDEN: Mr. President.
PRESIDENT BOOP: Yes, Commissioner Schleiden.
MR. SCHLEIDEN: Commissioner Mohr, I don’t believe there’s any science to present it to the Board on this particular issue. However, there was a demonstration. So the only thing we had to view was the social and political; therefore, we are looking at that issue from that standpoint.
Those people who advocate the use of this now have time, because we put it into committee, now have time to bring their case forward, and if it requires science, they’ll have that opportunity. I don’t think it has anything to do with allocations.
Thank you, sir.
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I offer the following 3 information items...
I'm new to the atlatl. The newspaper stories have peaked my interest. So I bought some and started learning all I could. I'm 59 years old, born and raised in Watsontown, Northumberland County. Currently living in Lancaster to be closer to my children and grand children. I'm a computer man by trade.
My #1 item...
I found this report to be the best one on the internet for the "science" of atlatls. It's all science facts. I hope that each member reads it. It compares the atlatl with an arrow, a .357 and a .30-06. Just great stuff! Here it is...
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HOW Hard Does It Hit?
A Study of Atlatl and Dart Ballistics
Daryl Hrdlicka
Jeffers Petroglyphs Historic Site
October 29, 2004
INTRODUCTION:
Anybody who has tried an atlatl and dart knows that it's a powerful combination (ancient people used it to hunt mammoth, after all). But nobody ever seems to know exactly HOW powerful it is -- on the internet, you will find pages that say it's anywhere from 3 times to 100 times more powerful than a spear thrown by hand. That's a lot of difference, and nobody ever says (or shows) how they came by their figure.
To settle it (and to find out which was nearest the truth), I sat down and made some calculations about different projectile weapons, including atlatl darts. In the end, I came up with three variables for comparison -- how hard it hits (kinetic energy), how hard it is to stop (momentum), and how effectively it penetrates (sectional density). These are explained in more detail later.
There are many other factors, of course. The sharpness of the point, its shape, and its diameter all make a difference. A wider blunt point will expend most of its energy simply pushing through the skin, while a narrower sharp one will slice through easily and go in deeper. And while an arrow is good for close range, it simply doesn't have the effective range of a .30-06. An atlatl has an even shorter effective range.
Since there can be (and have been) an infinite number of variations on projectile shape, weight, speed, range, etc., there is no realistic way to account for them all. That being the case, I'm just looking at these three main factors. That will give at least a general guideline to an atlatl's hunting effectiveness.
PROJECTILES:
I used a number of projectiles, both ancient and modern, in order to show where each ranks in terms of kinetic energy, momentum, and sectional density. NOTE: These are average weights, speeds, and diameters.
Light Spear (equivalent to a javelin): 2 pounds, 50 mph, 1" diameter
Heavy Spear (equivalent to a Roman pilum): 5 pounds, 25 mph, 1 1/2" diameter
Light Atlatl Dart: 3 ounces, 85 mph, 1/2" diameter
Heavy Atlatl Dart: 6 ounces, 70 mph, 5/8" diameter
Primitive Arrow: 500 grains, 165 fps, 3/8" diameter
Modern Hunting Arrow: 540 grains, 220 fps, 11/32" diameter
.357 Magnum handgun bullet: 125 grains, 1450 fps, .357" diameter
.30-06 rifle bullet: 180 grains, 2600 fps, .30" diameter
As you can see, bullets and arrows are measured in grains and feet per second (fps). Darts and spears are measured (if ever) by ounces and miles per hour. Since we need to use the same units of measurement to get any meaningful results, here are the conversion factors I used.
1 pound = 16 ounces = 7000 grains
1 ounce = 437.5 grains = 0.0625 pounds
1 mile per hour = 1.47 feet per second
KINETIC ENERGY:
Kinetic energy = 1/2 x Mass x Velocity^2
(Mass is the weight of the object (in pounds) divided by the pull of gravity (32.2 ft./sec/sec). Velocity is the change in position divided by the time in which the change occurs (the rate of speed).)
When an object is in motion, it has kinetic energy. When it strikes something, that energy is transferred. This is the basic force of impact - how hard the weapon strikes the target. Kinetic energy is measured in "foot pounds" (the energy needed to exert a one pound force for a distance of one foot).
KINETIC ENERGY CALCULATIONS:
In descending order
Projectile Weight Velocity Kinetic Energy
.30-06 Rifle 180 grains 2600 fps 2701 ft. lbs.
.357 magnum Pistol 125 grains 1450 583
Light Spear 2 pounds 73.5 167
Heavy Spear 5 pounds 37 106
Heavy Dart 6 ounces 103 62
Modern Arrow 540 grains 220 58
Light Dart 3 ounces 125 45
Primitive Arrow 500 grains 165 29
Kinetic energy was calculated as follows:
Light Dart:
KE = 1/2 x (lbs. / gravity) x (velocity in fps)^2
KE = 1/2 x (.1875 / 32.2) x (125 fps x 125 fps) = 45 foot pounds
.357 Magnum:
KE = 1/2 x ((125 / 7000) / 32.2) x (1450 fps x 1450 fps) = 583 foot pounds
Kinetic energy is very dependent on velocity. A bullet, because it is moving so fast, has incredible amounts. A .30-06 has nearly 100 times the kinetic energy of a primitive arrow. And yet Native Americans used those primitive arrows to hunt not only deer, but bison as well.
A rough guide for hunting effectiveness based on kinetic energy (this is an archery chart) is:
Kinetic Energy Hunting Usage
< 25 ft. lbs. Small game
25 - 41 ft. lbs. Medium Game (deer, antelope, etc.)
42 - 65 ft. lbs. Large Game (elk, black bear, wild boar, etc.)
> 66 ft. lbs. Toughest Game (cape buffalo, grizzly, etc.)
As you can see, both the light dart and the heavy dart seem weak compared to firearms, but they have more kinetic energy than the primitive arrows. Looking at the Hunting Usage chart, you can see that a heavy dart would be sufficient to bring down even the toughest game -- assuming it is in the effective range. For an atlatl, the effective range is perhaps 50 yards, and over 30 yards they will start losing velocity, which means less kinetic energy.
Kinetic energy is often used as the standard for projectile effectiveness, but a baseball (5.12 ounces moving at 95 mph) has 87 foot pounds of kinetic energy. It actually strikes harder than an atlatl dart, but I can't really see hunting a bison with a fast ball. While kinetic energy determines how hard an object strikes, it doesn't determine how far it penetrates. That is where momentum comes in.
MOMENTUM
Momentum = Mass x Velocity
Momentum is the tendency of an object in motion to STAY in motion. Anyone who has pushed a car in neutral and then tried to stop it will understand this -- the more momentum it has, the more resistance it will take to stop it. Momentum is measured in "slug feet per second".
MOMENTUM CALCULATIONS:
In descending order
Projectile Weight Velocity Momentum
Heavy Spear 5 pounds 37 fps 5.75 slug-feet/second
Light Spear 2 pounds 73.5 4.57
.30-06 180 grains 2600 2.08
Heavy Dart 6 ounces 103 1.20
.357 magnum 125 grains 1450 .80
Light Dart 3 ounces 125 .73
Modern Arrow 540 grains 220 .52
Primitive Arrow 500 grains 165 .37
Momentum was calculated as follows:
Light Dart:
Momentum = (.1875 pounds / 32.2) x 25 fps = ..73 slug-feet/second.
.357 Magnum:
Momentum = ((125 grains / 7000) / 32.2) x 1450 fps = .80 slug-feet/second.
Flesh normally has a density of about 1 gram per cubic centimeter. Hide is more dense, bone is about twice that (2 g/cc), and organs are less dense. Projectiles with a lower momentum, like the arrows, may have trouble penetrating thick hide and can be stopped fairly easily if they hit bone. Projectiles with a lot of momentum, like the spears, will go through hide, flesh, bone, and organs, penetrating until they encounter enough resistance to stop them. More momentum also means the projectile is less likely to be deflected by branches or underbrush, so it can be used in different types of terrain.
In addition, momentum is a factor in "knockdown". A heavy atlatl dart has enough momentum to knock a 40 pound animal completely off its feet and will definitely affect a larger animal. Objects with less momentum, like the arrows or the .357 magnum, will have a much smaller effect. (Movies and TV shows lie -- a handgun bullet simply will not knock a person off their feet. The difference in mass is too great. And if you did have a handgun that could do that, the recoil force would shatter the wrists of the shooter.)
You can see that the darts are much more effective in terms of momentum, even better than the .357 magnum. Mass and velocity are equally important in momentum, and darts have quite a bit of mass. It would take more resistance to stop them, which means they would be more effective at penetrating deeply enough into the target to hit a vital area.
But penetration also depends on where you hit. If you hit an animal in the ribs, most of the momentum will be lost getting through them. If you hit it in the stomach, the dart will penetrate much deeper. Arrows, with such low amounts of momentum, simply had to be aimed to where they could penetrate deeply enough.
But momentum alone isn't enough for calculating penetration -- if you filled a 5 gallon pail full of sand and fired both the .357 magnum and the primitive arrow at it, the bullet would be stopped by the sand, while the arrow would pass through completely. Our baseball, with 1.31 slug-feet/sec. of momentum, would simply bounce off. What makes the difference? Sectional density.
SECTIONAL DENSITY
Sectional Density = Weight /Diameter^2
(Weight is measured in pounds; diameter is measured in inches.)
A ping-pong ball thrown at a pop can will bounce off. A BB will go right through. What makes the difference? The sectional density. Even though they may weigh the same, in a BB the weight is much more concentrated. Since it is striking a smaller area on the target, more of the momentum is conserved, and it will penetrate deeper. Other factors being the same, a denser projectile will always penetrate more effectively than a lighter one. Sectional density is measured in pounds per square inch.
SECTIONAL DENSITY CALCULATIONS:
In descending order
Projectile Weight Diameter Sectional Density
Heavy Spear 5 pounds 1.5" 2.222 psi
Light Spear 2 pounds 1" 2.000
Heavy Dart 6 ounces .625" .960
Light Dart 3 ounces .5" .750
Modern Arrow 540 grains .344" .653
Primitive Arrow 500 grains .375" .508
.30-06 180 grains .30" .285
.357 magnum 125 grains .357 .140
Sectional Density was calculated as follows:
Light Dart:
SD = .1875 pounds / (.5" diameter x .5" diameter) = .750 pounds per square inch
.357 Magnum:
SD = (125 grains / 7000) / (.357" x .357") = .140 psi
Sectional density is why the arrow passes through the sand, the bullet is stopped by it, and the baseball bounces off. The primitive arrow, with .711 psi, is denser than a bullet., which means the momentum is conserved more efficiently. The baseball, with its high kinetic energy and momentum, has a sectional density of only .039 psi. The weight is spread out over such a large area that the momentum is easy to stop, meaning there is no penetration.
Atlatl darts are very effective in terms of sectional density. The weight of the long shaft is concentrated in the small diameter, making them more efficient than either arrows or firearms (even the mighty .30-06). This means that the momentum is conserved better, which means the darts will penetrate better.
CONCLUSION:
No one of the three factors we looked at is an indicator of hunting effectiveness by itself. All the weapons listed have been used for killing, and all have proven themselves effective. Atlatl darts do not have as much kinetic energy or momentum as firearms, but have a better sectional density. They are higher in all three factors than arrows, and arrows are known to be very effective weapons. There is very little you can't bring down with a well-placed arrow.
Is an atlatl as powerful as a .30-06? No. It has less kinetic energy (force of impact) and less momentum (penetration). It doesn't have anywhere near the effective range and is much harder to aim. But for tens of thousands of years, it was the primary hunting weapon on earth. Dart points have been found in mammoth bones, and they have been tested on modern elephant carcasses with impressive results. While it may not be as effective as a rifle, it is certainly effective enough. Just how dead do you need your supper?
Bibliography
Firearms ballistics information:
http://medstat.med.utah.edu/WebPath/TUTORIAL/GUNS/GUNBLST.html
"Arrow Penetration - Much Ado About Nothing?" by Dr. Mark Timney
http://www.bowsite.com/bowsite/features/practical_bowhunter/penetration/
"Understanding Arrow Penetration" by J.L. Spinks
http://www.alaskafrontierarchery.com/Articles.html
"Arrow Penetration" by Joe Tapley
http://homepage.ntlworld.com/joetapley/target.htm
"Airgun Ballistics" by Robert Beeman
http://www.beemans.net/airgun%20ballistics.htm
Atlatl and elephant information:
http://www.enteract.com/~mpavlac/sportscx.htm
"The Sectional Density of Rifle Bullets" By Chuck Hawks
http://www.chuckhawks.com/sd.htm
In addition, many thanks to Leroy Madden, who took the time to tutor me on physics and who helped me write this second version of the article. I literally couldn't have completed it without him.
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My #2 item...
Because of my computer background, researching databases of info is easy and this post got my attention. It's from www.huntingpa.com!
"In terms of hits on big game the atlatl retrieval rate has been in the high 90 percent range, which in my experience is better than I have done with bow hunting."
I have also learned the following on this site...see my post below.
I have been watching the PGC decision on hunting with atlatls and the animal rights (AR) people had the lobby to send it back to committee! They say it has no killing power...yet it has more hitting power then an arrow. They say you will not get what you hit, yet an Atlatl has a higher "hit and get" ratio then an arrow. The atlatl has a higher "miss clean rate" then an arrow and that is good not bad. So, the AR people should be saying OK to atlatls and out with bows...from their own logic that got the Atlatl sent back. They will not do that. It will be also...no more bows and arrows. And they win again has they did this time. I think the bow guys need to get with the atlatl guys or we both will be not hunting with our selected arm!
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My #3 item...
In February '06 I was asked to setup a live demo area for people to use the atlatl at the Christ Wesleyan Church's (Milton PA) Icebreaker. I did that and Channel 16 did a 6 min clip on the atlatl. This is an e-mail I sent to WNEP-16 the next day. Of significance was how well people did at their first try ever with the atlatl. For 5 1/2 hours with a steady line...no one had ever used it before. I also have 2 grand kids that I worked with and in 15 min. they were hitting my deer target...saying, this is great! I want to hunt with one of these. These "kids" were getting excited about hunting. That made me get reintegrated in hunting...I stopped buying a license for about 10 years...back into it now and would love to take this kids out with at atlatl. That's why I'm writing these e-mail!
I also teach a SR High Sunday School class and we are going to try the atlatls next week because of all the interest these "modern" kids have in this old technology. Maybe these "modern" kids will become PA Hunters!!!
See my WENP-17 e-mail below.
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I didn't get one picture on Saturday...was too busy! I had a line from 10:00 AM until 3:30 PM when the wind storm hit! Great day for CWC and Men's Ministry. I saw many Dad's spending time with their kids and just having a good time in the great outdoors. They told me they liked the one-on-one setup and many thanked me for spending so much time with each person who wanted to try it out!
I have only been into Atlatls for 2 months and I was surprised at how well many people hit the target after just throwing 4 times at the box and then at the target. Wow, that was great to see
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So, that is it!
I'm a little concerned about sending this to just the "GM, Comments" e-mail address at the PGC. I want to be sure all 8 members get this e-mail. So members...please just turn this around back to me if you do get to see it. Hope you do!!
Russ...
Russell W. Guthrie
Guthrie Strategy & Technology, LLC
1101 Central Manor Road
Lancaster, PA 17603
717-871-9763
717-871-9764 Fax
russguthrie@comcast.net
rguthrie@gsandt.com
www.gsandt.com