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Rifles, Reloading, Optics, Equipment
Reloading
Why do we ignore the horizontal?
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<blockquote data-quote="rcoody" data-source="post: 1167371" data-attributes="member: 91090"><p><span style="font-family: 'Times New Roman'">here is one man's thoughts</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'"><strong>THEORY</strong></span></p><p><span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">There are two independent types of barrel vibrations.</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">The</span></p><p><span style="font-family: 'Times New Roman'"></span><strong><span style="font-family: 'Times New Roman'">pressure inside the barrel causing it to expand and contract in a</span></strong></p><p></p><p><strong></strong></p><p><strong><span style="font-family: 'Times New Roman'"> </span></strong></p><p><strong><span style="font-family: 'Times New Roman'">harmonically defined fashion (much like the string on a violin vibrates when it is</span></strong></p><p> <strong><span style="font-family: 'Times New Roman'"></span></strong></p><p><strong><span style="font-family: 'Times New Roman'">plucked) as it moves along the barrel causes the first type of vibration</span></strong></p><p><strong><span style="font-family: 'Times New Roman'"></span></strong></p><p><strong></strong><span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'"></span><span style="font-family: 'Times New Roman'">. When the</span></p><p></p><p><span style="font-family: 'Times New Roman'"> </span></p><p><span style="font-family: 'Times New Roman'">bullet leaves the muzzle when it is at its smallest diameter, accuracy is improved. When</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">the muzzle has expanded and is larger than the minimum, it acts like a bad crown with</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">the bullet smaller than the bore. Formulas to calculate </span></p><p><span style="font-family: 'Times New Roman'"></span><strong><em><span style="font-family: 'Times New Roman'">Optimum Barrel Time </span></em></strong><span style="font-family: 'Times New Roman'">are</span></p><p></p><p><span style="font-family: 'Times New Roman'"> </span></p><p><span style="font-family: 'Times New Roman'">provided in the appendix. This vibration mode depends on only barrel length. With the</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">use of the </span></p><p><span style="font-family: 'Times New Roman'"></span><strong><em><span style="font-family: 'Times New Roman'">Quick Load and Pressure Trace </span></em></strong><span style="font-family: 'Times New Roman'">products barrel times can be estimated.</span></p><p></p><p><span style="font-family: 'Times New Roman'"> </span></p><p><span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">The</span></p><p><span style="font-family: 'Times New Roman'"></span><strong><span style="font-family: 'Times New Roman'">second and most significant type of vibration type </span></strong><span style="font-family: 'Times New Roman'">is the bending mode of</span></p><p></p><p><span style="font-family: 'Times New Roman'"> </span></p><p><span style="font-family: 'Times New Roman'">the barrel. Think of clamping a steel ruler to a bench and then bending and releasing the</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">free end. The ruler will vibrate based on its characteristics and the force applied to start</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">the vibrations. A gun barrel functions in the same, but much more complicated way.</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">In the case of our ruler one can write a differential equation of motion to describe</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">the motion, velocity and acceleration of any point on the ruler. To do this for the rifle</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">barrel is far more complicated.</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">Let's consider the series of events from the time the trigger is pulled until the</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">bullet leaves the muzzle. Each of the following events happens at a small, millisecond</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">time lag after the previous event.</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">a. The trigger is pulled to release the sear</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">b. The sear releases the firing pin</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">c. The firing pin moves forward, striking the primer</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">d. The primer and cartridge are driven forward</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">e. The primer ignites causing it to move rearwards, striking the bolt face</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">f. The powder begins to burn and causes the bullet to move forward</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">g. The bullet strikes the rifling and begins to spin</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">4</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">h. The action and barrel moves rearward in recoil until the recoil lug is stopped</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">by the stock</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">i. The entire rifle recoils</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">The list could go on, but the reader should get the point. Each of the events can be</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">described with a differential equation of motion, each spaced slightly different in time.</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">All of the differential equations need to be simultaneously solved to get a picture of the</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">barrel vibration. Solving the equations is not important, but knowing they exist is. What</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">the shooter sees is the sum of all these. You might ask why this is important. We will try</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">to answer that question shortly.</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">The barrel will vibrate with a number of modes or harmonics. Simply put, each</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">successive mode (harmonic) will cross the centerline (the nodal point) of the barrel one</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">more time than the previous mode (harmonic) and be at a higher frequency. For example</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">if the second mode (harmonic) were 445 cps the third mode might be 1,246 cps. As the</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">harmonics increase, the final crossing point gets closer to the muzzle. A good example of</span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'">this can be found on </span></p><p><span style="font-family: 'Times New Roman'"></span><strong><span style="font-family: 'Times New Roman'">Varmint Al's </span></strong><span style="font-family: 'Times New Roman'">web site </span><span style="font-family: 'Times New Roman'"><span style="color: #0000ff"><span style="font-family: 'Times New Roman'"><span style="color: #0000ff">www.varmintal.com</span></span></span></span><span style="font-family: 'Times New Roman'">. His barrel tuner</span></p><p></p><p><span style="font-family: 'Times New Roman'"> </span></p><p><span style="font-family: 'Times New Roman'"><a href="http://www.bostromgunsmithing.com/ImprovedRifleAccuracy.pdf" target="_blank">http://www.bostromgunsmithing.com/ImprovedRifleAccuracy.pdf</a></span></p><p><span style="font-family: 'Times New Roman'"></span> </p><p><span style="font-family: 'Times New Roman'"> </span></p><p> <span style="font-family: 'Times New Roman'"></span></p><p><span style="font-family: 'Times New Roman'"></span></p></blockquote><p></p>
[QUOTE="rcoody, post: 1167371, member: 91090"] [FONT=Times New Roman]here is one man's thoughts [B]THEORY[/B] [/FONT] [FONT=Times New Roman][/FONT][FONT=Times New Roman]There are two independent types of barrel vibrations. The [/FONT][B][FONT=Times New Roman]pressure inside the barrel causing it to expand and contract in a[/FONT][/B] [B] [FONT=Times New Roman] harmonically defined fashion (much like the string on a violin vibrates when it is plucked) as it moves along the barrel causes the first type of vibration [/FONT] [/B][FONT=Times New Roman] [/FONT][FONT=Times New Roman]. When the[/FONT] [FONT=Times New Roman] bullet leaves the muzzle when it is at its smallest diameter, accuracy is improved. When the muzzle has expanded and is larger than the minimum, it acts like a bad crown with the bullet smaller than the bore. Formulas to calculate [/FONT][B][I][FONT=Times New Roman]Optimum Barrel Time [/FONT][/I][/B][I][FONT=Times New Roman][/FONT][/I][FONT=Times New Roman][/FONT][FONT=Times New Roman]are[/FONT] [FONT=Times New Roman] provided in the appendix. This vibration mode depends on only barrel length. With the use of the [/FONT][B][I][FONT=Times New Roman]Quick Load and Pressure Trace [/FONT][/I][/B][I][FONT=Times New Roman][/FONT][/I][FONT=Times New Roman][/FONT][FONT=Times New Roman]products barrel times can be estimated.[/FONT] [FONT=Times New Roman] The [/FONT][B][FONT=Times New Roman]second and most significant type of vibration type [/FONT][/B][FONT=Times New Roman][/FONT][FONT=Times New Roman]is the bending mode of[/FONT] [FONT=Times New Roman] the barrel. Think of clamping a steel ruler to a bench and then bending and releasing the free end. The ruler will vibrate based on its characteristics and the force applied to start the vibrations. A gun barrel functions in the same, but much more complicated way. In the case of our ruler one can write a differential equation of motion to describe the motion, velocity and acceleration of any point on the ruler. To do this for the rifle barrel is far more complicated. Let’s consider the series of events from the time the trigger is pulled until the bullet leaves the muzzle. Each of the following events happens at a small, millisecond time lag after the previous event. a. The trigger is pulled to release the sear b. The sear releases the firing pin c. The firing pin moves forward, striking the primer d. The primer and cartridge are driven forward e. The primer ignites causing it to move rearwards, striking the bolt face f. The powder begins to burn and causes the bullet to move forward g. The bullet strikes the rifling and begins to spin 4 h. The action and barrel moves rearward in recoil until the recoil lug is stopped by the stock i. The entire rifle recoils The list could go on, but the reader should get the point. Each of the events can be described with a differential equation of motion, each spaced slightly different in time. All of the differential equations need to be simultaneously solved to get a picture of the barrel vibration. Solving the equations is not important, but knowing they exist is. What the shooter sees is the sum of all these. You might ask why this is important. We will try to answer that question shortly. The barrel will vibrate with a number of modes or harmonics. Simply put, each successive mode (harmonic) will cross the centerline (the nodal point) of the barrel one more time than the previous mode (harmonic) and be at a higher frequency. For example if the second mode (harmonic) were 445 cps the third mode might be 1,246 cps. As the harmonics increase, the final crossing point gets closer to the muzzle. A good example of this can be found on [/FONT][B][FONT=Times New Roman]Varmint Al’s [/FONT][/B][FONT=Times New Roman][/FONT][FONT=Times New Roman]web site [/FONT][FONT=Times New Roman][COLOR=#0000ff][FONT=Times New Roman][COLOR=#0000ff]www.varmintal.com[/COLOR][/FONT][/COLOR][/FONT][FONT=Times New Roman]. His barrel tuner[/FONT] [FONT=Times New Roman] [URL]http://www.bostromgunsmithing.com/ImprovedRifleAccuracy.pdf[/URL] [/FONT] [FONT=Times New Roman] [/FONT] [/QUOTE]
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Why do we ignore the horizontal?
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