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Recoil ?

Discussion in 'Shooting Related Threads' started by 635 G, May 31, 2009.

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  1. 635 G

    635 G Well-Known Member

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    At what speed does a 1 oz load equal the felt energy of a 11/8 oz @ 1145 FPS & 1200FPS.

    Thanx--Phil Berkowitz
     
  2. ink ball

    ink ball Member

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    A 1 oz load at 1270 fps is pretty close to the same recoil as an 1 1/8 oz load at 1145. A 1 oz load at 1330 fps is about the same recoil as an 1 1/8 oz load at 1200 fps.

    Here is a link that will allow you to calculate different variables.

    http://10xshooters.com/calculators/Shotgun_Recoil_Calculator.htm
     
  3. phirel

    phirel TS Member

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    For a quick, and reasonably accurate estimate, multiply the shot weight times the velocity. That is not a bad way to compare recoil.

    Pat Ireland
     
  4. tcr1146

    tcr1146 Well-Known Member

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    Pat,
    Unless physics has changed since I was there, it should be velocity squared times mass or in this case, weight! 1270 squared times 1 oz is much higher number than 1145 squared times 1.125?! Tom Rhoads
     
  5. phirel

    phirel TS Member

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    Tom- My quick estimation of relative recoil is actually a direct measurement of work, but it does a fair job of comparing recoil. Actual recoil involves mass times acceleration, but that is hard to calculate on the back of an envelope.

    Pat Ireland
     
  6. hmb

    hmb Well-Known Member

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    What planet you are shooting on should also be part of the equation. HMB
     
  7. KENENT1

    KENENT1 Active Member

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    Mars???


    tony
     
  8. dverna

    dverna Active Member

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    Yes,
    Men are from Mars.

    There is a book about that.

    Don

    PS Mr. Rhoads is correct - velocity squared
     
  9. Pocatello

    Pocatello Active Member

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    Force is mass times acceleration, but kinetic energy is not conserved in the "equal but opposite" physics law. As an obvious instance of this, think of shooting a rifle. In many common hunting loads the bullet's kinetic energy at the muzzle is in excess of 2000 foot pounds. If the rifle's kinetic energy were also 2000 foot pounds, it would do as much damage on the back end as the front, and shooting it would be as damaging at the back end as at the front.

    Newton says that force is the same for the gun as for the charge:

    M= mass of the gun, A=acceleration of the gun

    m=mass of the charge (shot/wad/powder), a=acceleration of the charge

    MA=ma, but in opposite directions

    Then the derivative with respect to time is the same: V=dA/dt, v=da/dt

    so momentum is the same: MV=mv

    Momentum is recoil that you feel.

    To answer the original question, 1 oz of shot weighs 437.5 grains, while 1 1/8 oz weighs about 492.2 grains. In my loads I use less than 20 grains of powder, but I load mild loads (16.5 grains of Clays for 1 oz, about 18.5 grains of International Clays for 1 1/8). I have not weighed the wads I use, so this is just a WAG - say about 25 grains for either the Figure 8 or TGT-12. So the rough charge weight for a one ounce load would be somewhere around 480 grains total, and for the 1 1/8 somewhere around 535 grains total. To convert to mass units one would need to divide by the acceleration of gravity, but since both sides are divided by that constant there is no net effect. So multiply the 1145 fps speed by the fraction 535/480 to get the comparable recoil speed of the one ounce load and get 1276 fps, very close to the answer ink ball supplies.
     
  10. BIGDON

    BIGDON Well-Known Member

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    If you spent more shooting then worrying about XxY=PDR squared your scores would be a hellava lot better.

    Don

    This horse has been beat, pummelled and stomped to death.
     
  11. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Don, yer cheerios taste a tad odd this mornin er whut?:) We like beatin up on some subjects and appreciate Larry's math skills too! Let us have our fun till it's time to shoot? BTW, I loved the bumper snickers a lot! :) Hap
     
  12. Neil Winston

    Neil Winston Well-Known Member

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    To add a bit to Pocatello's post, you can't (quite) treat the velocity of the wad/shot the same as the velocity of the powder.

    (one odd thought from Hatcher. At shot exit, the speed of the powder is half that of the shot. There are two ways to get this. One, the powder (now a gas, of course) is filling the bore, and so it's center of mass has only traveled half as far as the shot, and two, the powder-gas near the breech has traveled little-to-not-at all and the part near the shot is at shot speed, and so the average is about half shot speed.)

    But the gas is under pressure, and when the barrel is "uncorked" it rushes out and picks up speed. The result is that experiment is best matched by math when the weight of the powder is multiplied by about 1.25 in calculating the momentum imparted to the gun by the ejects. In Krag rifles use 1.5, in a Garand use 1.75.

    While Pocatello's distinction between conserved energy and momentum is _the_ answer to Tom R's post, I recall that there have been spotty published attempts to quantify the relationship between "real"
    and "perceived" recoil. One of the claims made was that if you want to guess how much recoil you will "experience" you shouldn't just flatly say that 5% more momentum will feel like 5% more recoil, but rather maybe do the energy-of-recoil calculation too (not just the momentum) and plan that what you feel may be about half-way between the two predictions.

    For example. Base case is a mass of 10 and a recoil velocity of 100. Then add powder to give a recoil velocity of 110.

    The mv calculation is that you now "get" , instead of 1000 whatevers, you get 1100 of them. By energy you would get 1221 of them. The best guess, according to the purported results of the test, is that you will report a recoil of about 1150. And I think this is about in line with what I feel. A Handicap shell, to me, seems to kick well in excess of what's predicted by the momentum analysis alone.


    When I say "purported" I'm signaling that the analysis of data you read in shotgun magazines is usually so suspect (if there be any data at all) you can't put much trust in it. In one published test, the experimental question was as the burning speed of powder was varied, was the perception of recoil differences the same for all types of shooters. "No" was the answer. Novice gunners thought the slow powders kicked less, while experienced sportsmen called the fast powders "softer shooting." (Or the other way around.) It sounded fine until you looked at the results as numbers, than then it was clear that the whole thing could be accounted for by chance, right to the point where you could have translated it to "novice and experienced coin flippers" and easily have gotten the same results.

    So my answer to Phil's opening question is "No one really knows but you can find out, kind of, by testing Handicap One ounce loads and comparing them to the others."

    Neil
     
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