When showing off your new Elephant rifle goes wrong

[Desperatezulu]

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.

 

[Inline6]

Some times pictures work better. I figure the load at 2150fps, and 100grs of powder. It's close enough for this experiment.

one barrel.

Both barrels

 

[akrifleman]

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.

Only if the second doubles simultaneously can you split the mass. Otherwise your calculations require the mass in motion at the time the second barrel fires.

 

[Desperatezulu]

Only if the second doubles simultaneously can you split the mass. Otherwise your calculations require the mass in motion at the time the second barrel fires.

Agreed- if you read the thread, you will see that the point was made about a simultaneous double discharge.

If we want to get more technical (and I don't think we do), we would need to factor in the effects of inertia of the system, the combined mass and velocity of the total ejecta and possibly even the jet effects of the gases leaving the barrels

 

[akrifleman]

Agreed- if you read the thread, you will see that the point was made about a simultaneous double discharge.

If we want to get more technical (and I don't think we do), we would need to factor in the effects of inertia of the system, the combined mass and velocity of the total ejecta and possibly even the jet effects of the gases

 

[akrifleman]

LoL. When I was younger I enjoyed the math. Now it was more a joke I figured you'd enjoy. Now the prospect of calculating not only the decay of the mass in motion vs the mass of the shooter, and the angular velocity of the twist sounds waaaay to much like my job. Pragmatically, I think doubling is usually a slipped finger and difficult to quantify, but more than double and less than quad.

 

[Daniel Cary]

8.75 pounds. Holy cow.

I once gave my 500S&W to a 16 year old, under recoil the barrel damn near hit him in the forehead. Big kid who shot often, I was shocked. Opened the cylinder and two rounds were fired. Nobody heard the second, they were fired that close together. Turns out the kid fired and then squeezed the grip, and trigger, for dear life. In doing he so he fired two rounds, almost at the same time.

Turns out the last bigbore he had fired was a single action 454. He got accustomed to dealing with the recoil by holding on for dear life with both hands, including his trigger finger.

That happened more than a few times with the 500 S&W .. I still could not figure "What, I'm doing wrong"? .. It's happened with others that shot it just as well.

 

[IvW]

I did not want to comment but....

Kids around, new rifle, "I wanted.to show off", you cannot even remember how many beers you had 12 or 15......
So by your own admission you where pissed with a new rifle showing off around a whole group of people with kids around....

You are a fool

 

[deewayne2003]

Man if you could harness that and pull off a well controlled pair at that distance ans place them within a couple of inches of each other, the impact on target would be truly impressive.

It is truly impressive.... I had an instant double happen with a .470NE while demonstrating the proper way to shoot one after some out of town guests demanded to shoot big bores at another person's property.

The load = 500gr Hornady bullet, 78gr. IMR3031, 2.0gr dacron, Winchester LRM primer.

This was an absolute spur of the moment adventure and running short on daylight we decided to make due with the targets on hand which were standard White Flyer clay pigeons(orange top) placed on a pond dam.

After a brief explanation to the spectators(who were all firearms owners) about the proper sight picture for the rifle, I took aim and BOOOOOM!

As the muzzle rises and the stock transfers energy into my body I distinctly remember thinking ......

"This feels different!" and as soon as I process this thought I also notice that I am having to replace my left foot and it is not behind my right foot.

When I opened the rifle both empty cases flew out, what I didn't know what this had been caught on cell phone video and you can see the double impact of bullets vaporize the clay pigeon as the dirt from the berm makes an impressive cloud and I can only image what it would have been like if we had only stopped to get a 10lbs bag of flower as a target!

Why the double fire?.... Ken Owen said it was a sear engagement issue because a screw backed out.

I always wondered what the true recoil velocity and ftlbs of that was?

 

[Backyardsniper]

Your contribution is appreciated as usual.....

I did not want to comment but....

Kids around, new rifle, "I wanted.to show off", you cannot even remember how many beers you had 12 or 15......
So by your own admission you where pissed with a new rifle showing off around a whole group of people with kids around....

You are a fool

 

[Backyardsniper]

It is truly impressive.... I had an instant double happen with a .470NE while demonstrating the proper way to shoot one after some out of town guests demanded to shoot big bores at another person's property.

The load = 500gr Hornady bullet, 78gr. IMR3031, 2.0gr dacron, Winchester LRM primer.

This was an absolute spur of the moment adventure and running short on daylight we decided to make due with the targets on hand which were standard White Flyer clay pigeons(orange top) placed on a pond dam.

After a brief explanation to the spectators(who were all firearms owners) about the proper sight picture for the rifle, I took aim and BOOOOOM!

As the muzzle rises and the stock transfers energy into my body I distinctly remember thinking ......

"This feels different!" and as soon as I process this thought I also notice that I am having to replace my left foot and it is not behind my right foot.

When I opened the rifle both empty cases flew out, what I didn't know what this had been caught on cell phone video and you can see the double impact of bullets vaporize the clay pigeon as the dirt from the berm makes an impressive cloud and I can only image what it would have been like if we had only stopped to get a 10lbs bag of flower as a target!

Why the double fire?.... Ken Owen said it was a sear engagement issue because a screw backed out.

I always wondered what the true recoil velocity and ftlbs of that was?

Off the subject but, I may need to try the 3031. I was a lite leery to try the stuffing but I have been running 94 gr of H4350 with the CEB bullets and it is shooting OK but not awesome. I am actually headed to the range now with a batch of them to try and see what they are really doing. I couldn't find any real data on the 3031 though. I'm using about a 3/4" piece of open cell 5/8" backer rod.

 

[C.W. Richter]

Recoil energy is not equal to the bullet energy.
Recoil momentum = bullet momentum (or more accurately recoil momentum would equal bullet momentum + charge momentum)
You're assuming recoil energy = bullet energy; this would be extremely painful.

and a great many things can be done to mitigate felt recoil, though no double was made to fire both triggers, although what was likely felt was the normal recoil energy, twice in quick succession and not both simultaneously. plus the beer (the likely causal agent.) Hemmingway would be proud, but he too had his double incident...

 

[375 Ruger Fan]

@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?

 

[RTG]

@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?

It's like a wife, pushing you towards her parents house. She is pushing you faster than you are moving, because you're a big dude (but not big enough to go to the bar instead).

Enough pushing and there you are, at their house.

 

[Inline6]

If you really want to see what it looks like with both barrels going off at the same time....I have a video of my son doing that.

 

[xausa]

I gained one important lesson from my experience: if I hold my rifle correctly, recoil is not going to injure me. My "go-to rifle" for thick skinned dangerous game was my wildcat .505 SRE. My 8 3/4 pound rifle propelled a 570 grain bullet at 2150 fps, with the following result:

Recoil Input Data Charge Weight: 95.0 gr Muzzle Velocity: 2150.0 ft/s Firearm Weight: 8.8 lb Bullet Weight: 570.0 gr Output Data Recoil Velocity: 27.1 ft/s Recoil Energy: 100.8 ft•lbs Recoil Impulse: 7.4 lb•s

23-Aug-22 15:18, JBM/jbmrecoil-5.1.cgi

On more than one occasion, I fired the entire contents of the magazine (3) following the initial shot as fast as I could manipulate the bolt and line up the sights again. On these occasions, I never noticed the recoil, and on one occasion I shot a playing card size group into the shoulder of a running Cape buffalo, while perched on a narrow ledge on a hillside several feet above the animal. On another occasion, I managed a difficult brain shot on an elephant from behind the ear, while stending on top of a termite mound. He collapsed immediately, allowing me to put a follow up shot through his heart.

 

[Red Leg]

Every now and then I fall to my knees and thank a merciful God and all the Saints that I no longer have to work with engineers.

 

[Backyardsniper]

Every now and then I fall to my knees and thank a merciful God and all the Saints that I no longer have to work with engineers.

You know me and you might get along after all

 

[Inline6]

Every now and then I fall to my knees and thank a merciful God and all the Saints that I no longer have to work with engineers.

Have to do it almost daily.

Kiss works the best.

 

[Tra3]

It's like a wife, pushing you towards her parents house. She is pushing you faster than you are moving, because you're a big dude (but not big enough to go to the bar instead).

Enough pushing and there you are, at their house.

Simplified concepts like this are how all engineering problems should be explained!