When showing off your new Elephant rifle goes wrong

Mark A Ouellette said:

100% correct!

I have participated in research and development tests where we had to fire weapons at precise amount of milliseconds between shots. A fire control system using computer controlled mechanical actuators would fire the machine mounted weapons. These shots where filmed at 10,000 frames per second and higher video. Despite a room full of electrical and mechanical engineers, we had to "dial in" the timing for the exact delay by observing the delay between shots. There are a lot of variables for this.

Obtaining a double discharge where both barrels reached peak pressure at the same time is difficult in a laboratory, and darn near impossible in the field.

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Mark A Ouellette said:

I had an 8 shotgun double on me twice one morning at a tower shoot. I wrote about it here previously. Fellow shooters only heard a extra load report, not boom-booms. With 52 lbs of recoil in each barrel, at 4x recoil, the 200 lbs recoil would have hurt me badly. It did not, well after I got my bearing from 52 lbs, plus 52 lbs recoil... Ouch but nothing broke, nor did it knock me on my butt.

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rookhawk said:

Thank goodness for best quality English engineering in your hands, eh?

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Backyardsniper said:

So...what had happened was, the local deer camp that I attend had a skeet shoot/Texas Holdem' gathering yesterday. This is a fairly standard issue event around here in the greater West KY area. Probably 12 or 15 of us invited to hang out at the local deer camp, cook, shoot a few clays, drink a bunch of beer, and lose money a good bit of money at the poker table. I wanting to show off my new double rifle, as you might imagine, there is a terrible shortage of 470 N.E. double rifles in the rural KY area, brought the rifle with me.
We had a rifle target set up and the kiddo's were shooting BB guns and 22's. So we decided to get out the double and give her a try. I put the rifle together and dropped 2 of the shiny nickel plated federal cases topped off with CEB solids into the barrel with a very satisfying "Plunk!" which drew some ooh's and ahh's and snapped it shut then I proceeded to draw down on the target with a relaxed manner that only 12-15 coor's banquet beers can produce and squeezed very gently on the front trigger. I was rewarded with what would have been possible the most impressive double tap that had ever been witnessed, and would have made the finest of tier one operators tip a hat in my direction, if those two bullets had landed in any reasonable proximity to each other . I'm my most relaxed state I had not applied quite enough grip on the rifle and doubled it. I would have readily blamed it on a rifle malfunction but it was not. I clearly felt my finger slip from one trigger to the other under recoil, which was solidified by the fact that my finger was indeed resting on the rear trigger when I returned the barrels to a horizontal position from thier then skywards orientation.
It was not as bad as one would imagine, I would not wish to repeat it regularly, but it was survivable ha ha. There was much confusion among the spectators as to whether this had been done intentionally and that was just how you operated one of these strange rifles. I explained to them that it was indeed not the normal method of operation. I then reloaded and did manage to fire a very pretty offhand pair at 25 yards that landed right at 1" apart squarely at 3 o'clock and 9 o'clock of a 1" bullseye at 25 yards. A few of the other guys shot it and a good time was had by all, and I won a few dollars playing bluebird, I then skipped partaking in the Texas Holdem' so as to maintain my winnings from the bluebird and a smidgen of my pride.

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Backyardsniper said:

May have to put your purse down for some of my posts.

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Desperatezulu said:

The Newtonian laws still apply. Maybe it helps to understand if we think about the behaviour of the rifle (keeping Newton's 3rd law firmly in mind) rather than the muzzle energy.
The rifle (10.5lb or whatever) has twice the amount of energy (force) applied to it (from 2 simultaneous discharges) therefore its recoil velocity doubles, because its mass is constant.
Add the rifle recoil velocity at double the single shot value into the formula F = 1/2m v^2 and it's clear how doubling the recoil velocity quadruples the recoil energy. Albeit not very intuitive!

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Desperatezulu said:

Eish guys - the physics are straightforward albeit not intuitive!

I'll try again...
The Law of conservation of momentum states that m1v1 = -m2v2
I.e. (mass of object 1 * vel of object 1) is equal to and opposite (hence the negative) the (mass of object 2 * vel of object 2)

Let's call object 1 the bullet and powder mass and object 2 the gun. We want to solve for the velocity of object 2 (the gun)
Therefore v2 = -(m1/m2)*v1
v2 is the recoil velocity, or the 'free' velocity of the gun.
Still with me?

V2 = -(39.88g/5000g) * 2000 ft/s
(I have assumed a 500gr bullet and 100gr of powder which equates to 38.88g. Gun weighs 5000g. I have made a big simplification on the velocity of the powder and bullet combo because technically the bullet may be going at 2000ft/s but the powder charge is going at something like 5000ft/s. So the value of m1v1 is actually higher and the recoil velocity would be higher than my simplified answer. But the underlying principle stands - the key factor here is that the mass of the bullet& powder doubles with a double discharge)

Thus V2 = -15.55 ft/s for the single discharge
Hope we're all agreed so far.

If we double discharge, the formula looks like this:
v2 = -((2*39.88)/5000) * 2000 = -31.9 ft/s
Note the "2" in bold above - this is because we have twice the mass of bullet and powder.
We see how the recoil velocity has doubled.
Hope I haven't lost the die hards still following

Now we need to calculate the recoil energy:
I think we're all agreed that the formula for calculating kinetic energy is:
KE = 1/2 mass * velocity^2
Or: recoil energy of gun = 0.5 * mass of gun * recoil velocity * recoil velocity

I hope I can cut to the chase and point out that a doubling (i.e. a factor of 2) of the recoil velocity, once squared, becomes a quadrupling (factor of 4) of the kinetic energy value.

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375 Ruger Fan said:

@Desperatezulu, you wrote: I have made a big simplification on the velocity of the powder and bullet combo because technically the bullet may be going at 2000ft/s but the powder charge is going at something like 5000ft/s.

How can this be? The powder charge is behind the bullet, correct?

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Bob Nelson 35Whelen said:

@Desperatezulu
I still don't see how the recoil velocity is doubled when bot cartridges give the same velocity with the same powder weight and projectile weight
If one cartridge has a recoil velocity of say 20fps how can another identical cartridge with a recoil velocity of 20fps give you a recoil velocity of 40fps if both ar recoiling at 20fps.
Double the powder charge and bullet weight but keep the recoil velocity the same. Recoil will still go up because both masses have increased but recoil velocity will remain constant.
Bob

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Recoil will still go up because both masses have increased but recoil velocity will remain constant.

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Flewis said:

If you guys need a volunteer to pull both barrels at once I’m here. Would be in the interest of science of course. You will have to supply the rifle as I would not use mine. I shot my brothers 12 bore shot gun several times that way and at the end of the day it was off face.

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Desperatezulu said:

With respect - not understanding something doesn't invalidate it.

Simple analogy - a twin engined jet aircraft: the velocity of gases out of the 'engine' is the same for both engines when running. Gas velocity out of the engines provides thrust, which is what makes the jet accelerate and sustains velocity during flight. Why does the plane need both engines to take off if the gas velocity from a single engine (half the thrust) makes the plane travel at the same velocity (or accelerate at the same rate) according to you? Your theory, as best I can decipher, is that one jet engine would accelerate the plane at the same rate as two, for the same given engine settings.


How does this work - how does 'recoil' go up if the velocity of the recoiling gun is unchanged?
Twice as much force is heading out of the barrels with a simultaneous discharge - Newtons Laws tell us that twice as much force must be experience in an equal and opposite direction (recoil) compared to a single discharge.
The force in this context is acceleration. If acceleration is doubled, does velocity remain the same?
(mass of the recoiling rifle is assumed constant in both scenarios)

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Randy Bo said:

Interesting…As a life-long Kentuckian I am familiar with: “dumb”, “inbred”, “redneck”, “hick” and “hillbilly”. What others might you add?

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