Long Range Hunting Online Magazine Exploding Prairie Dogs.....
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# Exploding Prairie Dogs.....

#8
08-23-2005, 08:31 AM
 Platinum Member Join Date: Jun 2001 Location: Potomac River Posts: 5,084
Re: Exploding Prairie Dogs.....

What you are describing is why the open ocean fisheries have been depleted by the commercial fishing operations. The high tech approach is simply devastating the fish populations in every ocean in the world.

Anyway back to pdogs. Somewhere in my computer I made some conservation of momentum calculations. Momentum is just the mass of the object multiplied times the veleocity of the object. A varmint bullet at high speed has a momentum of about 1.0 - 1.5. A prairie dog weighs about one pound so if you disintergrate you varmint bullet on him /or her the momentum is transferred to the pdog which then moves with a velocity of 1.0 to 1.5 feet per second. If you shoot low and hit it low then the moementum is applied a distance of about six inches (assuming the dog is 12 inches high) from the center of mass. This gives you a torque arm of six inches. Torque is angular momentum., This causes the pdog to fly and rotate.

Now then if you shoot a hundred pound deer with the same bullet you give the deer the same momentum of 1.0 so to get the speed at which the deer is slammed to the ground you must divide 1.0 by 100 pounds and you get a velocity of the deer of 0.01 fps - it moves one foot every one hundred seconds. For a 1000 pound moose of bufffalo you would impart a speed of 0.001 fps (i.e. he would not even twitch).

In all of this nonsense is the simple fact that a 55 grain varmint bullet will move a pdog wieghing one pound but if you want to move a deer weighing 100 pounds you would need to shoot a bullet weighing 100 times more - 5,500 gr bullet traveling at a speed of about 3500 fps. This would flip a deer over like a pdog. I believe this is about a 105 howitzer.

I suspect you already know most of this but maybe some of the kids can learn something about the difference between bullet energy and bullet momentum.
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The Smokin Fur Rifle Club
#9
08-23-2005, 11:44 AM
 Gold Member Join Date: Jul 2005 Location: East TX Posts: 773
Re: Exploding Prairie Dogs.....

Actually a .45-70 shooting 300 gr HP at 2450 fps will flip a deer and cause a massive explosion of flesh similar to those seen in the videos. I shot a doe two seasons ago at about 75 yds. Three vertebrae and the upper lobes of the lungs were scattered up to 12 feet in a persimmon tree, and she was lifted and thrown over a water-bar and back about six or seven feet. Imagine 1/2 to 2/3 of a regulation-sized basketball size piece of flesh being removed from a 100 lb whitetail doe to the spinal cord and that is what was missing. In all the carnage, her spinal cord was not severed, and I had to finish her off with 155 gr 40 S&amp;W to the brain region.
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Stephen
#10
08-23-2005, 12:01 PM
 Platinum Member Join Date: Jun 2001 Location: Potomac River Posts: 5,084
Re: Exploding Prairie Dogs.....

With the 45-70 at 70 yards you had an momentum of about 3.0 pounds-sec.
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The Smokin Fur Rifle Club
#11
08-29-2005, 09:37 PM
 Silver Member Join Date: Nov 2004 Location: GF Montana Posts: 467
Re: Exploding Prairie Dogs.....

[ QUOTE ]
<font color="purple">torque arm of six inches. Torque is angular momentum.,</font>

[/ QUOTE ]

You can only have a torque arm if you can sustain a shear, which the dirt obviously cannot. The conservation of momentum is essentially correct except you are dissipating a lot of energy in the dirt. By hitting the dirt you transfer more mass at lower velocity to the animals underbelly. A direct hit doesn't move the animal as far.
I used 165gr BT-HP out of my '06

Torque is R X F
Angular momentum deals with momentum around an axis (at least topologically speaking, depending on the number of dimensions).
#12
08-29-2005, 10:15 PM
 Silver Member Join Date: Nov 2004 Location: GF Montana Posts: 467
Re: Exploding Prairie Dogs.....

[ QUOTE ]
<font color="purple"> if you want to move a deer weighing 100 pounds you would need to shoot a bullet weighing 100 times more - 5,500 gr bullet traveling at a speed of about 3500 fps. </font>

[/ QUOTE ]

Shooting a deer with a 5.5 Kgr bullet at 3.5K FPS wouldn't move the deer much, it would punch a hole through him. Remember, when you shoot a gun, you get more momentum applied to your shoulder than the target gets. If the deer had armour plating, then yes it would go rolling.

Hold a box up and drop a brick into it and you will feel the momentum. Now shoot that box with a .22 rim-fire and the same box won't move.
#13
08-30-2005, 08:55 AM
 Platinum Member Join Date: Jun 2001 Location: Potomac River Posts: 5,084
Re: Exploding Prairie Dogs.....

Torque is R X F
Angular momentum deals with momentum around an axis (at least topologically speaking, depending on the number of dimensions).

At some point I need to figure out how to do the little quote box [img]/ubbthreads/images/graemlins/confused.gif[/img]

Yes and no. You are specifically correct but where you say "axis" I say "center of mass" My inertial frame refernce point is different from yours. And no I am not a total idiot - Just a partial idiot [img]/ubbthreads/images/graemlins/grin.gif[/img] "shear" is "force" and force is "mass" times "acceleration".
"Acceleration" divided by "time" is "velocity". The simplication I made from "F =force" ( impulse) to momentum is acceptable if we are doing a COMPARISON and assume the time function of transfer (acceleration) is equivalent between a deer and a prairie dog we can divide time out of the function and be left with velocity time mass and are back to momentum-( we both know that a deer is about 10 times thicker than a prairie dog and the time of transfer of momentum will create a different "force" equation but my belief is that this is trvial in the scheme of the calculation).

You have indirectly answered a question that had bounced around in my head. If your bullet has a downward trajectory when it strikes the dog then how do you get a dog to have upward motion(fly through the air)- answer - by hittng the dirt in front of the dog and causeing dirt/ bullet to fly upward and "lift" the dog. So I guess if you want some dramatic videos of dogs flying through the air then you would want to riccochet the bullets into them.

If you want to have some fun with math with your new rifle, and beleive any of the stuff I have said then I have some really interesting stuff in my computer on conservation of momentum and shooting elk. This is left over from my very polite and courteous disagreement with John M. Too bad the man could not stick to science and had to get to name calling.

Any way I think the bottom line is that we agree a person will need a really thin jacket and big hollow point on the 105 howitzer bullet to move a deer.
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The Smokin Fur Rifle Club
#14
08-31-2005, 09:59 PM
 Gold Member Join Date: Nov 2004 Posts: 877
Re: Exploding Prairie Dogs.....

I had the opportunity to eat lunch with a few folks some years ago that know more about bullets than i ever will. Lones Wigger, and T.D. Smith among them. The topic was raised concerning how a bullet (the vmax in particular) can cause the devistation they do on small critters. What followed was a complicated discusion that i left from understanding that one of the major factors in these types of things is the rotational forces the bullet experences once it begins to expand, and is no longer (relatively ) concentric. Just some food for thought.
a bullet fired at 4000FPS, from a 1:10 twist barrel is turing 288,000RPM at the muzzle. Im not sure how much force that generates when you have a small section of jacket and core pushed... say... .01" off center, but i know its enough to turn a pretty solid piece of metal into tiny flakes, and dust.

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