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A gun question: in a recent post there was mention of a torque or twisting of a high power rifle action. I am not familiar with

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  • A gun question: in a recent post there was mention of a torque or twisting of a high power rifle action. I am not familiar with

    A gun question: in a recent post there was mention of a torque or twisting of a high power rifle action. I am not familiar with this. What is the effect of this twisting? Does it have any affect on the shooter, right hand rifling twist and say a left or right hand shooter? I know snipers compensate for the rotation of the bullet and how it affects the bullet path. What is the effect of the torque on the action and the shot?

  • #2
    In mechanical engineering, the solution to a problem in dynamics is in the form of a force and a couple (torque).A brief,but concise,analysis follows...In this case, both are due to the bullet moving through the barrel.Drag due to the lands is in a straight line through the centerline of the barrel and is negligible compared to recoil.The torque (couple) depends on bullet diameter,mass,and profile.A large-diameter heavy bullet with a round nose produces the most torque.When you fire the rifle, the torque due to the bullet tends to rotate the rifle around the pivot points...your forestock and buttplate.That makes the end of the barrel decribe an arc, which translates into a bigger arc at the hitpoint.How big this error is depands on range.There are too many variables to predict the exact effect.Best to take your own rifle to the range and sight it in at various ranges.The cartridge will not rotate (for practical purposes)during firing,so no bullet torque will transfer to the action.

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    • #3
      Torque is more pronounced in a handgun firing a powerful cartridge, where you can feel the gun twisting in your hand in the opposite direction to the rotation of the bullet.
      It usually isn't noticeable in a rifle where you have a four-point contact holding the rifle in place.
      I suppose a handgun fired from a Ransom Rest would impart more twist to a bullet. Just my two cents.

      Comment


      • #4
        Very well stated Barnaby. I like your comment "The torque due to the bullet {rotation as it accelerates through the barrel} tends to rotate the rifle around the pivot points...your forestock and buttplate".

        The torque and the recoil forces combine to put significant pressure on the receiver that is generally holding the barrel in the rifle stock. If the barreled action is not precisely bedded within the stock, especially right behind the recoil lug, it is likely to be moved around within the stock by these forces. Because of this movement, each subsequent shot essentially puts the receiver in a slightly different position within the stock.

        This movement can cause changes in the barrel vibration and torqueing arc described. This in turn changes the impact point of the bullet down range. Imagine the bullet exiting at 12:00 in the muzzle arc on the first shot and at 3:00 on the next shot as the arc is modified due to changing receiver position within the stock.

        There is no noticeable affect to the shooter as long as the action is in the stock (if you hold a .458 Win by the barrel as you fire the barreled action sans stock, you will feel it).

        This barrel vibration and torqueing is why groups generally improve with the addition of a barrel resonator or with glass/pillar bedding. This is also why muzzle brakes (with their extra muzzle weight and recoil reduction) may have significant impact on bullet impact point while in many cases actually improving the accuracy.

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        • #5
          DakotaMan you are right!
          I took the stock off my .458 Win and went out in the backyard just now. If you hold the barrel in your hand while touching one off the torque is noticeable. The recoil is a little worse.
          I hope everyone had a great Thanksgiving!

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          • #6
            I followed Barnaby right up to the last sentence.
            So, i gleaned from the answers, the torquing is the movement of the action within the stock support system, or is it along the longitudinal line of the action itself, or both?
            Chuckles, be careful doing that you could hurt yourself. Come to think of it, I did fire a '06 one time with a broken stock when I had to - that was no fun at all.

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            • #7
              Jimbo -

              "Torque" is the angular twisting force created by the acceleration of the bullet through the lands,transferred through the barrel to the receiver, and through whatever anchors it to the stock, and resisted and damped by your hands and shoulder.It is not only affected by mass and diameter of the bullet,but also by velocity and twist rate.The only torque of the action is due to inertia as its mass resists the turning motion of the receiver.If this causes any independent motion of the action,the firearm is unsafe to shoot anyway.

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              • #8
                I get the possible movement within the stock.
                -
                Somewhere I got the impression people were saying the steel of the action itself was twisting. That is the part I am trying to clarify. It is hard for me to imagine the steel twisting, but then for instance, the early '03's were noted for having soft steel and possibly that twisting was what was happening to them.
                Just my curiosity at work.

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                • #9
                  WoW this stuff is getten deep....Pass me that last Drum stick!
                  Lol

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                  • #10
                    jimbo -

                    Sounds like a material problem to me.

                    But I guess a couple of more things need to be said...

                    It would be nearly impossible to reproduce the axis about which the rifle rotates,as it depends upon how hard you grip it with either hand and how hard you pull the stock against your shoulder.And this will affect the radius of the arc through which the end of the barrel moves due to off-axis torqueing.The barrel is going to release the bullet in some direction tangent to the arc,and the arc radius determines the tangential velocity which determines the hitpoint error due to the torque.As the bullet clears the lands, it is touching well behind the center of mass of the bullet.The rise of the barrel does the same thing.Add these two vectors pushing behind the center of mass, and the bullet tends to want to swap ends,mostly "stabilized" by the spin,butt the effect is that it pushes the bullet off in some direction with a wobble not unlike a poorly passed phutbol. Add to that inconsistencies of mass production and nonconcentricities of bullet manufacturing,and you will suspect that DakotaMan shot that group with a drill press.Just kidding.Some things aren't worth worrying about and this is one of them.

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                    • #11
                      jhjimbo now that you mention it I do have a slight bruise from the palm of my hand to my elbow where the tang dug in a bit.
                      It was still worth it as I had not realized what a problem this torque issue was causing. The deer kept dying but many of them were making it up to 30 yds from where they were shot.

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                      • #12
                        Oddly, I think I followed most of that. Not bad for a fool of my caliber. Thanks for digging so deep Jimbo. Much appreciated!

                        Comment


                        • #13
                          So the bottom line is: we snug up our stock screws (with a torque wrench) and move out.

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                          • #14
                            Assuming that the twist and barrel threads were in the same direction; Could that same torque theoretically twist a barrel to a point of starting to unthread it? Or, if threaded in opposing directions, could it be always tightening the barrel to the receiver?

                            Comment


                            • #15
                              99, I just learned this year that Weatherby actually has a lbs.inch specification for the screws on the Mark V stock. Haven't checked it yet since it shoots so good right now.
                              Thanks Barnaby and Dakota for the explanation.
                              I have another technical question but I will hold off so others can post some questions.

                              Comment

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