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Rifles, Reloading, Optics, Equipment
Reloading
Ballistic Coefficient (BC)
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<blockquote data-quote="abinok" data-source="post: 126038" data-attributes="member: 16"><p>Dave tooley did some testing some time back putting amax tips in some other bullets. he figured out that the tips produced a more consistant BC bullet to bullet, with a slightly higher bc for the batch compared to un tipped bullets.</p><p></p><p>This is also where all our information about meplat trimming started.</p><p></p><p>Part of the reason most of the tipped bullets won't shoot with the SMK and J4 bullets, has to do with the simple fact that these bullets aren't assemled with the same care that companies like Berger, and Sierra place on their match bullets. Add to that that things like jacket quality are built into the bullet by the mfg of the jacket, and the bullet assembler has little controll over it.</p><p></p><p>As to how other materials affect BC... they do it through changing the SD. If you could take a bullet shape, and hold it as the constant, any materials lighter than lead will lower the SD, and things heavier than lead will raise it. Higher SD with the same form factor will raise BC, and lower SD with the same will lower it. </p><p></p><p>As far as where in the bullet the lead and other materials are located... there is some effect to BC, primarily as it effects the relationship of the bullets Center of Gravity, in relation to its Center of Pressure. Im gonna keep thsi really simple... CP behind the CG, and the bullet will be drag stabalized, and will fly point forward without being spin stabalized. CP in front of CG, and the bullet will try to fly backwards unless its spun, and if its not spun fast enough it will tumble because it can't damp all the torque that was imparted to it by the rifeling... so iw will never settle into stable base forward flight. Now then, our bullets have the CP in front of the CG, and this means that as they encounter a croswind, the bullet will be deflected, but that deflection will also effect how it is being gyroscopically stabilized, and it is the additional frontal area that is created as a result of the bullet torque relative to its flight path that decrease measured BC.</p></blockquote><p></p>
[QUOTE="abinok, post: 126038, member: 16"] Dave tooley did some testing some time back putting amax tips in some other bullets. he figured out that the tips produced a more consistant BC bullet to bullet, with a slightly higher bc for the batch compared to un tipped bullets. This is also where all our information about meplat trimming started. Part of the reason most of the tipped bullets won't shoot with the SMK and J4 bullets, has to do with the simple fact that these bullets aren't assemled with the same care that companies like Berger, and Sierra place on their match bullets. Add to that that things like jacket quality are built into the bullet by the mfg of the jacket, and the bullet assembler has little controll over it. As to how other materials affect BC... they do it through changing the SD. If you could take a bullet shape, and hold it as the constant, any materials lighter than lead will lower the SD, and things heavier than lead will raise it. Higher SD with the same form factor will raise BC, and lower SD with the same will lower it. As far as where in the bullet the lead and other materials are located... there is some effect to BC, primarily as it effects the relationship of the bullets Center of Gravity, in relation to its Center of Pressure. Im gonna keep thsi really simple... CP behind the CG, and the bullet will be drag stabalized, and will fly point forward without being spin stabalized. CP in front of CG, and the bullet will try to fly backwards unless its spun, and if its not spun fast enough it will tumble because it can't damp all the torque that was imparted to it by the rifeling... so iw will never settle into stable base forward flight. Now then, our bullets have the CP in front of the CG, and this means that as they encounter a croswind, the bullet will be deflected, but that deflection will also effect how it is being gyroscopically stabilized, and it is the additional frontal area that is created as a result of the bullet torque relative to its flight path that decrease measured BC. [/QUOTE]
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