I asked what Time it was

[Ray B]

I was told how to build a clock. On another post it was stated that firing both cartridges in a double rifle resulted in quadrupling the recoil of a single cartridge. It is given that since the gun weighs the same, an increase in recoil would be an increase in the guns velocity, so solving for 1/2MxV2 for a single cartridge, then for a double firing would give two totals that could be compared, basically is one twice or four times the other? All the detail of powder velocity etc just add needless precision to the basic question: Does a double double the recoil or quadruple the recoil? a follow-up from curiosity: if it quadruples, where does the extra energy come from?

 

[grand veneur]

I have to honestly admit that I don't know anything about this. I can only report on practical experience because my DR caliber 577 Nitro Express once doubled. Whether the recoil was double or quadruple stronger was difficult to say. It was a fact that I was lying on my back, holding tight my DR in my hands and on the front of my chest.

 

[BourbonTrail]

1/2 mV^2 is kinetic energy. It’s derivative is 2(1/2)mV —> mV.

mV is momentum. Momentum equation is used for determining the resulting speed (and force) of the rifle recoil. m(rifle)V1- m(rifle)V0 = Force of recoil = m(bullet)V1 - m(bullet)V0. (Rifle weight changes by the amount of powder and bullets that exit the barrel).

If you double the weight of the bullet (2 bullets) you don’t quadruple the force. Felt recoil may be more than 2x, but that has more to do with powder burn rate, stiffness of the gun, angular momentum, and gas jet effects. Pure linear momentum should (roughly) double.

 

[shootist~]

JBM - Calculations - Recoil

www.jbmballistics.com

Letting JMB Ballistics do the math, and inputting 11 lb Rifle, 400 grain bullet and 100 grain powder per load:

One barrel - Recoil Energy = 59.0 Ft Pounds
Double Fire - Recoil Energy = 235.8 Ft Pounds, (=4X or close enough).

Recoil Velocity went from 18.6 to 37.1 ft/s (= 2X +/- rounding)
Recoil Impulse went from 6.3 to 12.7 lb*s (= 2x +/- rounding)

 

[Ray B]

One barrel - Recoil Energy = 59.0 Ft Pounds
Double Fire - Recoil Energy = 235.8 Ft Pounds, (=4X or close enough).

There's the question:

Both bullets fired separately yield 59 ft lbs
so the total of both fired separately would be 118 ft lbs
But when fired together yield 236 ft lbs

Where does the additional 118 ft lbs of energy come from?

 

[Wyatt Smith]

This all interesting. It Must have to do with weight of the rifle. If I doubled the weight of a rifle, would it cut the recoil by half, or more? ILikewise would a five pound 500 Jeffrey recoil twice as much as a 10 pound 500 or more? I think more, but I am not certain.

 

[Aaron N]

I have been thinking about this since the formulas started getting thrown around. Now my physics education ended after high school, but hear me out.

In the thread this started, the rifle didn’t “double” simultaneously, but it was more of a double tap. A second shot following the initial. Now in this case, would the energy not be two impulses of the same energy, the second seeming amplified due to poor positioning, By the time the second trigger is pulled, the initial energy transfer from the rifle to the shooter should have been complete, and the shooters momentum decelerating (even if only a tiny bit)? If we look at the situation down range, and say two bullets producing 5000ft-lbs of energy each hit a Buffalo 0.5s apart, we wouldn’t call that a single 10000ft-lb impact would we?

This is how I view the situation from a very basic point of view. Please be gentle if I’m way off base!

 

[shootist~]

If you google SAAMI free recoil energy, you will find a SAAMI pdf of the Long Version of the formula the Britts arrived at in 1929. *One piece* of that formula is: (Bullet Weight x Velociity) / (7000 x Rifle Weight in pounds) Squared

Do the calculation, then double the bullet weight (only) and do it again. The second result will be about 4 times the first.

That does not answer the question, but it does point to where it comes from.