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Relationship of Pressure & Recoil

Discussion in 'Uncategorized Threads' started by Portagee Shooter, Jul 12, 2008.

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  1. Portagee Shooter

    Portagee Shooter Member

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    I would like to where I can find articles or information on shell pressure and it's relationship to recoil. Any knowledge would be appreciated.
    Thanks, Lyle
     
  2. Recoil Sissy

    Recoil Sissy Well-Known Member

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    Portagee Shooter:

    The section titled "Notes on Recoil" found on page 38 of the Hodgdon Basic Reloaders Manual (2002) includes some text and a formula to calculate recoil. The following comment is a direct quote from that text.

    "Unfortunately, too many shooters think that pressure has an effect on recoil. In truth, it doesn't. It is not included in the formula for calculating recoil...".

    Simply stated, Hodgdon doesn't think there is a relationship between pressure and recoil.

    sissy
     
  3. Easystreet

    Easystreet Well-Known Member

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    Lyle,

    There is no relationship of pressure to recoil. Sissy told you right.
     
  4. Chango2

    Chango2 Active Member

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    F=MxA
     
  5. Harold

    Harold TS Member

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    Let's be more specific. Pressure is what pushes the shot out the barrel and the gun back toward your shoulder. In that respect, it is related. However, the published pressure in your reloading manual is a peak pressure and cannot be used to determine the energy that is imparted to the recoiling gun by the F=MA formula.

    Traditionally, the recoil number calculated is free recoil energy. This is the kinetic energy that would be imparted to your gun if it was hanging by a pair of wires and free to recoil. This number can be calculated from the gun weight, projectile weight, projectile velocity, powder weight and powder gas velocity. An assumption is usually made of the velocity of the powder gas. The formula you generally run across is for military rifles like the 30-06, and is not accurate for shotguns. The effect of the powder gas relative to charge weight in a shotgun is small though, so that doesn't much matter.

    Free recoil energy is a handy number to calculate, but it is not the only thing to consider. The recoil blow can be softened by various methods like soft recoil pads, spring devices in your stock, etc. Gas operated semi-automatics spread the blow out over time, making the recoil feel softer.

    Some people think that slow burning powders work like a semi-auto, spreading the recoil out over time and softening the felt recoil. Slow burning powders develop lower peak pressure than fast powder, for a given velocity. People swear they can tell the difference, but this has never actually been proven.

    The recoil reduction of a semi-auto actually tends to prove the opposite. The gas semi-auto action is locked, just like a fixed breech gun, until the wad passes the pressure port. That's long, long after the pressure peak is past. If you had already felt the recoil at the pressure peak, the semi-auto action would do nothing to reduce it. You cannot un-feel the recoil after it is already felt.
     
  6. phirel

    phirel TS Member

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    Harold- Is there a relationship between the area under a burning rate curve for a specific powder and the free recoil energy produced ?

    Pat Ireland
     
  7. Harold

    Harold TS Member

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    Pat, there is a relationship, but the area is not proportional to the energy. The curve you are referring to , I think, has pressure as a function of time. The area under the curve would have units of pressure times time.

    Work is a form of energy and is defined as force multiplied by distance. This is the work that will be converted to kinetic energy. The work done by the burning powder against the bolt face of your gun will be equal to the force multiplied by distance the bolt face moves. If you assume the ID of the shell case and bore of the gun form a perfect cylinder, then the force will be equal to the pressure multiplied by cross-sectional area of the bore. So you could convert the pressure to a force and the area under the curve would be force times time. That still doesn't give you foot-pounds of energy. You have to know how far the gun moved in each time interval.

    I suppose you could take the curve and superimpose another calculated curve of gun displacement. Each interval on the curve you could calculate the gun position and how far it moved based on F-mA and the formula for displacement from Newton's equations. Then you could integrate under the force-displacement curve to get the kinetic energy. What you would find is that the early pressure peak does not impart as much energy as the later portion of the pressure curve because the peak happens while the gun is relatively still. No movement=no work=no kinetic energy.
     
  8. shot410ga

    shot410ga Well-Known Member

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    Well, I guess I'm one of the one's that can feel the change in a 1250fps load at 10,500 psi and one at 8600 psi. There is a SUBSTANTIAL reduction in the recoil that I feel. I don't care what the engineers say, shoot a heavy load using 700x, then shoot the same load using 7625. You will feel a recoil reduction, too.
     
  9. maclellan1911

    maclellan1911 TS Member

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    I think what you are feeling is a push rather than a punch with the different powders. to push X amount of weight out of the barrel at the same FPS requires the same amount of force. No?
     
  10. birdogs

    birdogs TS Member

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    Pressure is exerted in all directions simultaneously, that is against the chamber walls, and the breech face as well at towards the front of the shell (where there is little resistance). This is why it is not a component of recoil. Recoil is defined as the force exerted to the rear of the gun when the ejecta (bullet, shot, wad etc.) is propelled forward.
     
  11. spitter

    spitter Well-Known Member TS Supporters

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    Can't help you with an article about pressure v. recoil, but in the recent issue of Shooting Sportsman (May/June) there is a very easy to understand article about the effects of velocity, wt of the ejecta (wad, shot charge), wt of powder charge and the wt of the gun and its relative effects on actual recoil.

    Bottom line was to lighten up and/or use a heavier firearm to reduce actual recoil in an effort to avoid unintended effects of recoil (flinching etc...).

    While it mentioned reduction devices to reduce perceived recoil, the article was mainly about the former.

    Jay
     
  12. phirel

    phirel TS Member

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    flincher100- You must have seen something in Harold's reply that I did not.

    shot410ga- When you state that you can feel the recoil difference between a slow and a fast powder that the difference between slow and fast, with regard to powder burning, is between 3/10,000 and 7/10,000 of a second.

    There is a greater difference in recoil between two shells that differ only in charge weight by 1 shot. When you are shooting a box, not every shell has exactly the same number of shot. Can you feel the recoil difference between the lighter and heavier shot charges when you shoot a box of factory loads?
    Reloads are most likely more inconsistent in charge weight than factory shells.
    Also, not every shell has exactly the same amount of powder. You should be able to tell these relatively large differences if you can distinguish between a few ten thousandths of a second.

    Pat Ireland
     
  13. motordoctor

    motordoctor Shoji Tabuchi in Branson

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    A friend sent this to me. I'm not into math but will share what he sent. As the velocity increases the recoil increases as it does with an increase in weight of the shot and decrease in the weight of the gun.

    Weight of Ejecta in grains [shot, wad and powder] X velocity in ft/sec. Divide this by 7000 [7000 grains in one pound] = Units of momentum.

    Momentum [recoil] divided by the weight of the gun in pounds = velocity of the recoil in ft/sec.

    he said that anything below 96 is hard to take and over 120 is reasonable. I have not used thsi information and only pass it on as I received it.


    motordoc
     
  14. zzt

    zzt Well-Known Member

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    That's a bogus argument Pat. One varies with time, the other with intensity. It is quite reasonable to suppose it is easier to perceive differences in one more readily than in the other. Life is full of such examples.
     
  15. hmb

    hmb Well-Known Member

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    There is a relationship between pressure and recoil. If there is no pressure then there is no recoil. And if there is alot of pressure there is recoil. This seems like a relationship to me. HMB
     
  16. tburrey

    tburrey Member

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    I have a 391 Beretta and there is a world of difference in recoil with it using the same shells as there is in my BT99 or Remington 870. My friends have shot my semi and they too are amazed at the difference in recoil. Also,I can tell a world of difference between hot loads and soft loads in any of my trap guns. I just know what works and if my shoulder is sore at the end of the day. Tom
     
  17. maclellan1911

    maclellan1911 TS Member

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    found this website, does this help any??
     
  18. Portagee Shooter

    Portagee Shooter Member

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    I have heard in various discussions that the two were not necessarily tied together, and the comments mentioned allow one to gain a lot of information, form their own opinions and make our decisions.
    Thank you Gentlemen, I appreciate your help.

    Lyle
     
  19. shot410ga

    shot410ga Well-Known Member

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    Pat: Try the loads I suggested (700x & 7625), then tell me you don't feel a differance. Your a Green Dot guy. Try a 1250fps GD at 10,500, then a load of 7625 at 1250fps. Maybe, recoil is perceived, who knows. But, you will feel less recoil with the 7625.
     
  20. larryjk

    larryjk Member

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    I'm not sure how the mathematicians explain it with a formulae, but there cannot be recoil without pressure. Pressure is what makes the bullet (shot) go down the barrel. Remember Newton, for each action there is an opposite and equal reaction. We calculate this using the bullet velocity and mass. Velocity is a direct relationship to pressure.
     
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