Barrel Movement - Page 2


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Old 01-11-2014, 08:21 PM   #11
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Wood and steel will never be affected the same way by a shock.

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Old 01-11-2014, 08:25 PM   #12
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Originally Posted by dteed4094 View Post
I have always thought and told; any movement between the stock and the action is detrimental to consistency hence accuracy. I understand the harmonics but the more you reduce barrel whip, the more consistent your groups will be.
all barrels when fired have harmonics. the rifling is the key to a barrels accuracy. the rifling will affect the barrel harmonics when a round is fired. the barrel when shot heats up and heat will affect the barrel harmonics as well.

with the stock and action you are looking for a solid foundation. if there is movement between the two, then accuracy will suffer. accuracy comes from consistency in all the variables when shooting. everything with the rifle is consistent. everything about the shooter is consistent and everything about the ammo is consistent.


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Old 01-11-2014, 08:49 PM   #13
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the amount of movement or barrel whip doesnt matter if it does it the exact same way everytime.

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Old 01-11-2014, 08:50 PM   #14
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I have always thought and told; any movement between the stock and the action is detrimental to consistency hence accuracy. I understand the harmonics but the more you reduce barrel whip, the more consistent your groups will be.
That's correct, that's what a good bedding job does - improve the mechanical accuracy by dampening the whip. Good precise bedding is better than no bedding (free float), but no bedding is better than poor bedding (random points of barrel/stock contact).

With a genuinely free floating barrel AT LEAST the stock does not make things worse by touching the barrel here and there. If it does, every shot will cause variable harmonics ---> larger groups.
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Old 01-11-2014, 08:52 PM   #15
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the amount of movement or barrel whip doesnt matter if it does it the exact same way everytime.
i have even read in the past, that different weight bullets and different powder charges change the barrel harmonics to some degree, hence why some loads are more accurate than others.
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Old 01-11-2014, 09:02 PM   #16
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i have even read in the past, that different weight bullets and different powder charges change the barrel harmonics to some degree, hence why some loads are more accurate than others.
thats correct.

not all barrel cartridge combinations do well with bedding bedding a rifle stock can be a negative depending on materials. a bedded wood stock will change properties with humidity and temperature while bedding a synthic has typically good results if done correctly.

what you bed isnt the barrel but the reciever stiffening it and damping vibrations.

a poorly floated barrel that contacts the stock on vibration is worse than clamping the stock in a barrel band.

it all boils down to materials and who is doing the work. most stocks that come with guns off the shelf are pretty crappy which is why there is a huge aftermarket stock selection of manufacturers...
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Old 01-11-2014, 09:13 PM   #17
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thats correct.

not all barrel cartridge combinations do well with bedding bedding a rifle stock can be a negative depending on materials. a bedded wood stock will change properties with humidity and temperature while bedding a synthic has typically good results if done correctly.

what you bed isnt the barrel but the reciever stiffening it and damping vibrations.

a poorly floated barrel that contacts the stock on vibration is worse than clamping the stock in a barrel band.

it all boils down to materials and who is doing the work. most stocks that come with guns off the shelf are pretty crappy which is why there is a huge aftermarket stock selection of manufacturers...
and every rifle is different as well. some even like a little pressure pad at the fore end to gain accuracy.

personally i bed my rifles with about the first 3-4" of the barrel with the action and free float the remaining portion of the barrel with good results. one Remington M700 in 30-06 i did, went from about 3/4" groups down to just over 1/4" groups after bedding the stock this way.
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Old 01-11-2014, 10:12 PM   #18
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I've always known that the barrel vibrates when fired but I would have never guessed you see the movement just by applying pressure with your hands. Interesting!
Yes, it surprised me too. I also knew that barrels bend and vibrate when firing but didn't know you can cause it to happen and see deflection by pushing up and down or sideways with your hand. Like I said, the Sendero barreled action is solidly planted in a full length aluminum bedding block and still you can see the relative motion of the barrel with the stock. And after 550+ plus rounds through the Sendero, I know the rifle is accurate so I guess the motion is not a problem.
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Old 01-11-2014, 10:47 PM   #19
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Easiest way to picture it is to think of the barrel as a spring. It will move in three directions when a shock load (bullet fired) is applied and the oscellate as is goes back to its resting state.

It is compressing a small amount from the bullet being accelerated. This is very small +-0.0001 or less since steel is very strong in compression.

It is torqued around the surface of the barrel by the mechanical action of the rifling acting on the accelerating bullet. Think of twisting both ends opposite dirrections. Again very small, steel tubes are a strong form to resist torque.

Finally the barrel will whip up and down, or left to right. This is caused by harmonics of the above forces, but is the most easily seen since the long thin tube bends easiest in this direction. Sometimes as much as +-0.002 on magnum rifles.

Free floating the barrel and bedding the action solid is the best way we have found to get "consistent" barrel movement and shot placement. The barrel springs the same way each time as long as the shock load is the same. This gets the bullet to strike the same area each time...

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Old 01-11-2014, 11:11 PM   #20
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Yes, it surprised me too. I also knew that barrels bend and vibrate when firing but didn't know you can cause it to happen and see deflection by pushing up and down or sideways with your hand. Like I said, the Sendero barreled action is solidly planted in a full length aluminum bedding block and still you can see the relative motion of the barrel with the stock. And after 550+ plus rounds through the Sendero, I know the rifle is accurate so I guess the motion is not a problem.
Your hand does not flex the barrel like a tuning fork. It only shifts the stock relative to the barreled action (or you could say it vice versa) This is a mere free play. It does not correspond to the barrel oscillations caused by firing a projectile through it. Those are two different things. They may well coexist, but they are not the same.

It is true that the ballistics of a given projectile and the physical characteristics of the barrel are a unique combination that result in more or less "barrel whip". The barrel, as any system, will oscillate with a greater amplitude at some frequencies than the others. That is why a given firearm is known to "like" some ammo and "dislike" the other. No theory can fully predict the accuracy of your rifle. Certainly not the "free play" in the stock. It may not "feel right" but is a poor predictor of accuracy in itself.


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