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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Long range barrel profile
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<blockquote data-quote="Fiftydriver" data-source="post: 100702" data-attributes="member: 10"><p>Bart B,</p><p></p><p>To say a barrel only flexes vertically is a bit strange to me. How a bullet being forced to rotate as it is driven down a bore only produces vertical forces on the barrel does not make any sense to me personally.</p><p></p><p>I am not sure what you were referring to as far as the flexibilty of a heavy barrel compared to lighter barrel but if you are saying they both flex the same amount or have the potential to flex the same amount you are sorely mistaken.</p><p></p><p>As a gunsmith, I have the somewhat unique ability to mount barrels up in the lathe all the time. My chambering techniques is to hole the muzzle in the chuck and support the breech end with steady rest while chambering.</p><p></p><p>While setting up a barrel this way I can leave the barrels unsupported only being held by the muzzle. A light contour barrel will flex DRAMATICALLY more then a heavy contour. In fact, with a barrel length of 28 to 30" you will see these lighter contour barrels "droop" under their own weight until supported by the steady rest.</p><p></p><p>The heavier contours flex very little in comparision and once you reach around a #7 contour there is very little if any flexing that is noticable.</p><p></p><p>This is the same if the barrel is reversed as well for fitting a muzzle brake.</p><p></p><p>Now I am not sure you are referring to this in your post as I did not wish to read that far into it but if your talking about barrel rigidity you are incorrect.</p><p></p><p>I am not speaking with clinical laboratory test experience, just real life, in the shop and on the range experience which I often find much more useful and valuable then what is printed from laboratory testing!!</p><p></p><p>You must consider many variable that you are not when determining how a barrel will flex, whip or vibrate under live fire testing. Here is a short list that I hope you are including in your test data or your results will be flawed:</p><p></p><p>-Receiver thread diameter</p><p>-Receiver thread length</p><p>-Receiver thread fit</p><p>-Receiver thread taper amount if any(should not be)</p><p>-Receiver thread squareness</p><p>-Recoil lug squareness if present</p><p>-Barrel thread fit</p><p>-Barrel thread diameter</p><p>-Barrel thread length</p><p>-Barrel thread squareness</p><p>-Barrel shoulder squareness</p><p>-Chamber axial alignment</p><p>-Bore axial alignment</p><p>-Bullet run out</p><p>-Bullet velocity</p><p>-Bullet weight</p><p>-Bullet concentricity</p><p>-Bullet contruction</p><p></p><p>Ya see these reasons are why a custom rifle will often out shoot a factory rifle by a huge margin. There is alot more to accuracy then barrel stiffness you are correct in that, BUT, with all things equal, a heavy barrel will consistantly out perform a light barreled rifle over a string of shots over a given period of time.</p><p></p><p>Certainly there are exceptions to this rule but on average, the results are very easy to see.</p><p></p><p>If all of these aspects are not perfectly tuned for each of the test barrels you will not get consistant accurate data of what a barrel does when a bullet is driven down the barrel.</p><p></p><p>If you say that this is just a practical test to show the basic harmoinic patterns in a barrel, I can then say that putting bullets on target will do the exact same thing but in the case of a rifle shooter, the data corrected on target is much more valuable then how one engineering test tells you which barrel will vibrate compared to another.</p><p></p><p>Simply put, go to a local BR match and see what they are using for barrels. Generally for 100 and 200 yard BR matches you will see very heavy, very short(20-22" barrel lengths) barrels chambered for very low intenstity rounds shooting relatively light weight bullets. All in an attempt to limit as much barrel vibration as possible from shot to shot. They get groups in the .1s which is not practical with lighter, longer barrels with heavier bullets at higher velocities, why? The reason is obvious!! </p><p></p><p>Good Shooting!!</p><p></p><p>Kirby Allen(50)</p></blockquote><p></p>
[QUOTE="Fiftydriver, post: 100702, member: 10"] Bart B, To say a barrel only flexes vertically is a bit strange to me. How a bullet being forced to rotate as it is driven down a bore only produces vertical forces on the barrel does not make any sense to me personally. I am not sure what you were referring to as far as the flexibilty of a heavy barrel compared to lighter barrel but if you are saying they both flex the same amount or have the potential to flex the same amount you are sorely mistaken. As a gunsmith, I have the somewhat unique ability to mount barrels up in the lathe all the time. My chambering techniques is to hole the muzzle in the chuck and support the breech end with steady rest while chambering. While setting up a barrel this way I can leave the barrels unsupported only being held by the muzzle. A light contour barrel will flex DRAMATICALLY more then a heavy contour. In fact, with a barrel length of 28 to 30" you will see these lighter contour barrels "droop" under their own weight until supported by the steady rest. The heavier contours flex very little in comparision and once you reach around a #7 contour there is very little if any flexing that is noticable. This is the same if the barrel is reversed as well for fitting a muzzle brake. Now I am not sure you are referring to this in your post as I did not wish to read that far into it but if your talking about barrel rigidity you are incorrect. I am not speaking with clinical laboratory test experience, just real life, in the shop and on the range experience which I often find much more useful and valuable then what is printed from laboratory testing!! You must consider many variable that you are not when determining how a barrel will flex, whip or vibrate under live fire testing. Here is a short list that I hope you are including in your test data or your results will be flawed: -Receiver thread diameter -Receiver thread length -Receiver thread fit -Receiver thread taper amount if any(should not be) -Receiver thread squareness -Recoil lug squareness if present -Barrel thread fit -Barrel thread diameter -Barrel thread length -Barrel thread squareness -Barrel shoulder squareness -Chamber axial alignment -Bore axial alignment -Bullet run out -Bullet velocity -Bullet weight -Bullet concentricity -Bullet contruction Ya see these reasons are why a custom rifle will often out shoot a factory rifle by a huge margin. There is alot more to accuracy then barrel stiffness you are correct in that, BUT, with all things equal, a heavy barrel will consistantly out perform a light barreled rifle over a string of shots over a given period of time. Certainly there are exceptions to this rule but on average, the results are very easy to see. If all of these aspects are not perfectly tuned for each of the test barrels you will not get consistant accurate data of what a barrel does when a bullet is driven down the barrel. If you say that this is just a practical test to show the basic harmoinic patterns in a barrel, I can then say that putting bullets on target will do the exact same thing but in the case of a rifle shooter, the data corrected on target is much more valuable then how one engineering test tells you which barrel will vibrate compared to another. Simply put, go to a local BR match and see what they are using for barrels. Generally for 100 and 200 yard BR matches you will see very heavy, very short(20-22" barrel lengths) barrels chambered for very low intenstity rounds shooting relatively light weight bullets. All in an attempt to limit as much barrel vibration as possible from shot to shot. They get groups in the .1s which is not practical with lighter, longer barrels with heavier bullets at higher velocities, why? The reason is obvious!! Good Shooting!! Kirby Allen(50) [/QUOTE]
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