Gents:
Here is an article from 1937 about double rifles by Elmer Keith. Quite an interesting read.
Enjoy!
Cal

Cool article. Thanks.

However, I’ve always wondered how they could estimate the velocity back then without chronographs and such.

quote:

Originally posted by DCS Member:
Cool article. Thanks.

However, I’ve always wondered how they could estimate the velocity back then without chronographs and such.

I will be pleased to tell you.
As far back as the US Revolution and before it is simple, really.

Fire a lead projectile at a metal plate.
The weight of the projectile is known (back then it was a ball).
The distance to the metal plate is known.
The weight of the metal plate is known.

The metal plate is suspended with an indicator that has small graduations to tell how much the plate moved.

Using the projectile weight, distance, and how far it moved the metal plate, the velocity can be calculated. I looked but I can't find the formula just now. Perhaps someone here can assist.

Cal

quote:

Originally posted by cal pappas:

quote:

Originally posted by DCS Member:
Cool article. Thanks.

However, I’ve always wondered how they could estimate the velocity back then without chronographs and such.

I will be pleased to tell you.
As far back as the US Revolution and before it is simple, really.

Fire a lead projectile at a metal plate.
The weight of the projectile is known (back then it was a ball).
The distance to the metal plate is known.
The weight of the metal plate is known.

The metal plate is suspended with an indicator that has small graduations to tell how much the plate moved.

Using the projectile weight, distance, and how far it moved the metal plate, the velocity can be calculated. I looked but I can't find the formula just now. Perhaps someone here can assist.

Cal

I am no scientist or physicist, but it still seems hard to be within a few hundred FPS.

No one wore hearing protection then, but let me know if if wrong. I'm not saying it's even an exact science now. I'll believe MV with a chrono, but when stated at 500 yards I scratch my head. I've only shot one animal over 400, but I was injured and angry.

Muzzle energy is just a calculation, but based on MV. I can't say I believe much on the back of a box, but use redneck holdover.

Silly musings, but I still believe a valid question.

Regardless, thanks for the read.

Ballistic pendulum. Wiki will give you all the info. Ideally you want the pendulum to capture the bullet. Our physics teacher in high school used to bring in his Colt Woodsman and let the kids set one up and do the math in the physics class room (this was in Los Angeles). By the time I graduated I think the principal had decided that wasn't such a great idea and stopped the 'experiment'. The kids thought it was neat.
C.G.B.

I really enjoyed that article, Cal, and with exception of his 9.3x74 velocity, found it mostly rang true.

The pic of Elmer firing the 600 NE looked almost as though he was shooting at a high pheasant

Hello Cal:

Thanks for the reprint--great information from a wonderful writer.

Dave Manson

Thanks Cal.
I have always been a Keith fan and have all the books that he wrote, but this article was new to me and both fun and informative to read. Makes me want to go shoot an elk with my .405 double rifle.

From Wiki:









A ballistic pendulum is a device for measuring a bullet's momentum, from which it is possible to calculate the velocity and kinetic energy. Ballistic pendulums have been largely rendered obsolete by modern chronographs, which allow direct measurement of the projectile velocity.

Although the ballistic pendulum is considered obsolete, it remained in use for a significant length of time and led to great advances in the science of ballistics. The ballistic pendulum is still found in physics classrooms today, because of its simplicity and usefulness in demonstrating properties of momentum and energy. Unlike other methods of measuring the speed of a bullet, the basic calculations for a ballistic pendulum do not require any measurement of time, but rely only on measures of mass and distance.[1]

In addition its primary uses of measuring the velocity of a projectile or the recoil of a gun, the ballistic pendulum can be used to measure any transfer of momentum. For example, a ballistic pendulum was used by physicist C. V. Boys to measure the elasticity of golf balls,[2] and by physicist Peter Guthrie Tait to measure the effect that spin had on the distance a golf ball traveled.[3][4]


Contents
1 History
2 Mathematical derivations
2.1 Simple derivation
2.2 Robins' formula
2.3 Poisson's formula
2.4 Ackley's ballistic pendulum
3 References
4 Bibliography
5 External links
History[edit]

Ballistic pendulum (1911)
The ballistic pendulum was invented in 1742 by English mathematician Benjamin Robins (1707–1751), and published in his book New Principles of Gunnery, which revolutionized the science of ballistics, as it provided the first way to accurately measure the velocity of a bullet.[2][5]

Robins used the ballistic pendulum to measure projectile velocity in two ways. The first was to attach the gun to the pendulum, and measure the recoil. Since the momentum of the gun is equal to the momentum of the ejecta, and since the projectile was (in those experiments) the large majority of the mass of the ejecta, the velocity of the bullet could be approximated. The second, and more accurate method, was to directly measure the bullet momentum by firing it into the pendulum. Robins experimented with musket balls of around one ounce in mass (28 g), while other contemporaries used his methods with cannon shot of one to three pounds (0.5 to 1.4 kg).[6]

Robins' original work used a heavy iron pendulum, faced with wood, to catch the bullet. Modern reproductions, used as demonstrations in physics classes, generally use a heavy weight suspended by a very fine, lightweight arm, and ignore the mass of the pendulum's arm. Robins' heavy iron pendulum did not allow this, and Robins' mathematical approach was slightly more complex. He used the period of oscillation and mass of the pendulum (both measured with the bullet included) to calculate the rotational inertia of the pendulum, which was then used in the calculations. Robins also used a length of ribbon, loosely gripped in a clamp, to measure the travel of the pendulum. The pendulum would draw out a length of ribbon equal to the chord of pendulum's travel.[7]

The first system to supplant ballistic pendulums with direct measures of projectile speed was invented in 1808, during the Napoleonic Wars and used a rapidly rotating shaft of known speed with two paper disks on it; the bullet was fired through the disks, parallel to the shaft, and the angular difference in the points of impact provided an elapsed time over the distance between the disks. A direct electromechanical clockwork measure appeared in 1848, with a spring-driven clock started and stopped by electromagnets, whose current was interrupted by the bullet passing through two meshes of fine wires, again providing the time to traverse the given distance.[2]

Mathematical derivations[edit]
Most physics textbooks provide a simplified method of calculation of the bullet's velocity that uses the mass of the bullet and pendulum and the height of the pendulum's travel to calculate the amount of energy and momentum in the pendulum and bullet system. Robins' calculations were significantly more involved, and used a measure of the period of oscillation to determine the rotational inertia of the system.

Simple derivation[edit]
We begin with the motion of the bullet-pendulum system from the instant the pendulum is struck by the bullet.

Given
g
g, the acceleration due to gravity, and
h
h, the final height of the pendulum, it is possible to calculate the initial velocity of the bullet-pendulum system using conservation of mechanical energy (kinetic energy + potential energy). Let this initial velocity be denoted by

{\displaystyle K_{initial}={\begin{matrix}{\frac {1}{2}}\end{matrix}}(m_{b}+m_{p})\cdot v_{1}^{2}}

Taking the initial height of the pendulum as the potential energy reference


{\displaystyle (U_{initial}=0)}, the final potential energy when the bullet-pendulum system comes to a stop


{\displaystyle U_{final}=(m_{b}+m_{p})\cdot g\cdot h}

So, by the conservation of mechanical energy, we have:[8]


{\displaystyle v_{1}={\sqrt {2\cdot g\cdot h}}}
We can now use momentum conservation for the bullet-pendulum system to get the speed of the bullet,

v_{0}, before it struck the pendulum. Equating the momentum of the bullet before it is fired to that of the bullet-pendulum system as soon as

Wow! Thanks to all for answering my question. That’s pretty wild.

Thanks Cal. I remember these all those years ago. I went looking and found some unpublished Elmer Keith photos of Elmer and Doc DuComb and the hunters from the Snake River trip in "Hell, I Was There". Found one of Doc and Jack O'Connor posing with 4 full curl ram heads. Those were the days. His granddaughter was a close friend.

Great article. My favorite quote:

"The .600 is decidedly not an ideal lady's rifle"

Yep, Ballistic Pendulum, and they are remarkably accurate. I built one for my high school physics project, and brought my .22 to school to demonstrate it. The principal kept the rifle in his office for me when I was not in my physics class. The resident state trooper came to class to supervise the experiment, and I shot my .22, his .357 Magnum, and the .22 Magnum he carried as a backup gun into the pendulum. It was a very different time!

Years ago I bid on one of Elmer’s WR double rifles, the 470 IIRC, that Holt’s had for auction.

As I was in the bush in Tanzania I had to put in a bid and wait until I had connection to find out the result. It sold way above estimate upper price. But I did manage to get the information on it.

Same thing with Selous’ nice little single H&H that Bill Jones bought IIRC.

I have always enjoyed reading Kieth's description of the .375 2-1/2" Flanged Lancaster double and his loading adventures getting it regulated. At one point years ago I ended up with a Lancaster single (not oval bored) in .375 2-1/2" and it shot very well for me, including on a bison in SW Kansas not far from Dodge City.

Thanks for posting. It's nice to see the prices and thoughts from 1937.

Ken

Elmer was the man.

How he made it through life without shooting somebody is incredible, as he didn’t take shit off anybody and seemed to have dared them to cross him quite a bit.