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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Please help me with some ballistics calculations
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<blockquote data-quote="TRexF16" data-source="post: 2266744" data-attributes="member: 108912"><p>My new Christensen Mesa 6.5 CM is doing great. Even during the barrel break-in phase, two sub 1/2 MOA loads have emerged:</p><p>- 120 NBT over 45/H4350 for 3000 FPS</p><p>- 139 Scenar over 41.5/H4350 for 2700 FPS</p><p>I have run both of these using G7 BC's measured by Bryan Litz, .214 for the 120 BT and .285 for the 139 Scn. I used a program I am used to, the Burris Ballistics to run the trajectory and drift numbers, (out to 800 yards, with a 10 MPH crosswind, and 200 yard zero) and am surprised by one aspect of the results, which I would appreciate some backup by folks familiar with more sophisticated programs. Here's what did NOT surprise me:</p><p>- the 120 wins the velocity race out to 650 yards and then the 139 carries greater velocity beyond that.</p><p>- the 120 wins the energy race to 250 yards, and then the 139 carries greater energy beyond that.</p><p>- the 120 always wins drop, having an 8.5" advantage at 600 yards. The advantage increases to 16" at 800 yards</p><p>and here's what surprised me:</p><p>- the 139 ALWAYS wins drift, and its advantage builds to 4" at 600 yards, increasing to 8" at 800 yards.</p><p>I had expected, given the 300 FPS MV advantage, that the 120 would have less drift over the first couple hundred yards. This program shows the 120 has a 20 msec. (.020 sec) TOF advantage to 200 yards. That's pretty significant. Yet the program still shows the 139 having a 0.3" drift advantage at 200 yards.</p><p>Does this sound right?</p><p></p><p>Much appreciated,</p><p>Rex</p></blockquote><p></p>
[QUOTE="TRexF16, post: 2266744, member: 108912"] My new Christensen Mesa 6.5 CM is doing great. Even during the barrel break-in phase, two sub 1/2 MOA loads have emerged: - 120 NBT over 45/H4350 for 3000 FPS - 139 Scenar over 41.5/H4350 for 2700 FPS I have run both of these using G7 BC's measured by Bryan Litz, .214 for the 120 BT and .285 for the 139 Scn. I used a program I am used to, the Burris Ballistics to run the trajectory and drift numbers, (out to 800 yards, with a 10 MPH crosswind, and 200 yard zero) and am surprised by one aspect of the results, which I would appreciate some backup by folks familiar with more sophisticated programs. Here's what did NOT surprise me: - the 120 wins the velocity race out to 650 yards and then the 139 carries greater velocity beyond that. - the 120 wins the energy race to 250 yards, and then the 139 carries greater energy beyond that. - the 120 always wins drop, having an 8.5" advantage at 600 yards. The advantage increases to 16" at 800 yards and here's what surprised me: - the 139 ALWAYS wins drift, and its advantage builds to 4" at 600 yards, increasing to 8" at 800 yards. I had expected, given the 300 FPS MV advantage, that the 120 would have less drift over the first couple hundred yards. This program shows the 120 has a 20 msec. (.020 sec) TOF advantage to 200 yards. That's pretty significant. Yet the program still shows the 139 having a 0.3" drift advantage at 200 yards. Does this sound right? Much appreciated, Rex [/QUOTE]
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Please help me with some ballistics calculations
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