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Thread: Recoil

  1. #1

    Default Recoil

    In IPSC it is generally thought that a 40 S&W recoils less than a 45. Why is this?

    We all shoot to an identical Power Factor(Bullet weight in grains x bullet speed in Foot per second divided by 1000). This means that a 185 gr bullet must do 950 f/sec to reach a Power Factor of 175.

    Why wold the perceived recoil be less in a 40 than with a 45 in identical guns?

  2. #2
    Craig's Avatar
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    Default Re: Recoil

    Hi Johann

    Interesting post here, never really thought about this. What you say is very true regarding Power Factor. I suppose the bullet diameter may have an effect on recoil, but not sure on this? If this does, I'm assuming the .45 would have less recoil, as its slower? Do different calibres have a different type of recoil, would this then affect the perceived recoil?

    Anyone one else have any ideas here?
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  3. #3

    Default Re: Recoil

    For 3 years I worked on the answer "It just is" but now I would lie to know why. All the top shooters have gone to 40 and in my club a guy went up by about 10% just by changing. So there is something there,I just do not know what.

  4. #4
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    Default Re: Recoil

    Quote Originally Posted by Johann the Horrible
    Why wold the perceived recoil be less in a 40 than with a 45 in identical guns?
    Think it is something to do with pressure. The pressure in the 40 will be higher.....

  5. #5
    Moderator SSP's Avatar
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    Default Re: Recoil

    Quote Originally Posted by CJ
    Think it is something to do with pressure. The pressure in the 40 will be higher.....
    How would higher pressure equal less felt recoil?
    Cattle die, kindred die, every man is mortal:
    But I know one thing that never dies,
    the glory of the great dead.
    Havamal

  6. #6
    Mark Gogos
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    Default Re: Recoil

    Ok. The long-winded, scientific version:

    Recoil, in common everyday language, is considered the backward kick or force produced by a gun when it is fired. In more precise scientific terms, this force is equal to the time derivative of the backward momentum resulting when a gun is fired.

    The backward momentum is equal to the mass of the gun times its reverse velocity. This backward momentum is equal to the sums of the two forward momentums by the law of conservation of momentum and is due to and equal to the projectile's mass times its velocity added to the mass of the escaping gases, burnt propellant, unburnt propellant, and other gases, times their respective velocities. Provided that enough information is known for how all the velocities vary versus time, it becomes theoretically possible to determine all the accelerations versus time, and hence to calculate the total recoil force versus time. The force associated with the recoil may thus be calculated by using the law of conservation of momentum, provided that enough information regarding changes in momentum versus time is known. In practice, however, it is often easier simply to measure the recoil force resulting for a given load, rather than to estimate all the variations occurring in momentum versus time.

    For small arms, the way in which the shooter perceives the recoil, or kick, can have a significant impact on the shooter's experience and performance. For example, a gun that "kicks like a mule" is going to be approached with trepidation, and the shooter will anticipate the recoil and flinch in anticipation as the shot is released. This leads to the shooter jerking the trigger, rather than pulling it smoothly, and the jerking motion is almost certain to disturb the alignment of the gun and result in a miss.

    This perception of recoil is related to the momentum associated with a particular gun. The total force of recoil is associated with the momentum of a gun, the momentum being the product of the mass of the gun times the reverse velocity of the gun. A heavier gun, that is a gun with more mass, will manifest the momentum by exhibiting a lessened acceleration, and, generally, result in a lessened perception of recoil.

    One of the common ways of describing the felt recoil of a particular gun/cartridge combination is as "soft" or "sharp" recoiling; soft recoil is recoil spread over a longer period of time, that is at a lower acceleration, and sharp recoil is spread over a shorter period of time, that is with a higher acceleration. With the same gun and two loads with different bullet masses but the same recoil force, the load firing the heavier bullet will have the softer recoil, because the product of mass times acceleration must remain constant, and if mass goes up then acceleration must go down, to keep the product constant.

    Keeping the above in mind, you can generally base the relative recoil of firearms by factoring in a number of figures such as bullet weight, powder charge, the weight of the actual firearm etc.

    Basically: The bigger and slower the bullet (like a .45) the longer the gun itself takes to accelerate and reset in your hand. The smaller and faster the bullet (like a .40), the faster the gun will accelerate and reset in your hand, thus the perception of less recoil.

    Go to: http://handloads.com/calc/recoil.asp
    and compare the ammo between eachother. The .40 (180grn Bullet) and .45 (230grn bullet) fired from the same weight gun (2.6lbs) have similar maximum recoil speeds, but are slower / faster to acceleration and reset because of their respective velocities, powder charges and jet effect. It's the same as having a needle pushed slowly into you as opposed to a quick in-and-out jab to the same depth with the same needle. Which feels worse?

  7. #7

    Default Re: Recoil

    Forget about recoil. Live with it. Worry more about muzzle flip.

  8. #8
    Moderator SSP's Avatar
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    Default Re: Recoil

    Quote Originally Posted by para
    Forget about recoil. Live with it. Worry more about muzzle flip.
    +1

    I don't even notice anymore.
    Cattle die, kindred die, every man is mortal:
    But I know one thing that never dies,
    the glory of the great dead.
    Havamal

  9. #9
    Mark Gogos
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    Default Re: Recoil

    Quote Originally Posted by SSP
    Quote Originally Posted by para
    Forget about recoil. Live with it. Worry more about muzzle flip.
    +1

    I don't even notice anymore.
    And that's the short version..... ;D

  10. #10
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    Default Re: Recoil

    Muzzle flip.........

    Shoot more often...you'll get used to it. ;D

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