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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
chart probems
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<blockquote data-quote="BryanLitz" data-source="post: 317788" data-attributes="member: 7848"><p>Bud,</p><p>I think the problem may come from using the advertised G1 BC(s).</p><p>I haven't measured the G7 BC for the 140 MK (I do have the 142 MK). </p><p>Based on Sierra's advertised G1 BCs, this bullet should have a <strong>G7 BC of 0.270*.</strong> </p><p></p><p>I've generated the table below using that G7 BC and the following inputs;</p><p></p><p>MV = 2935 fps</p><p>I added 5 fps for velocity lost in the 10' from muzzle to target. This isn't a big deal considering there's probably more error than that in the Chrony.</p><p></p><p>Temp = 59 deg F</p><p>Pressure = 26.33 inHg (standard pressure at 3500 ft)</p><p>Sight Height = 1.68"</p><p>Zero range = 100 yards</p><p></p><p>Note that the bullet path in the table is -375.87" at 1125 yards.</p><p>That's equal to 31.9 MOA. You said you observed 31.2 MOA at that range, a difference of 0.7 MOA. </p><p></p><p>You said your chart showed more drop; 33.4 MOA at that range. What BC did you use to generate that chart?</p><p></p><p>How does the bullet path in the chart below compare to your records at other ranges?</p><p></p><p> Range Velocity Trajectory TOF Drift</p><p>(yards) (fps) (inches) (sec) (inches)</p><p> 0 2935 -1.68 0.0000 0.00</p><p> 25 2896 -0.86 0.0257 0.00</p><p> 50 2857 -0.31 0.0518 0.00</p><p> 75 2818 -0.02 0.0782 0.00</p><p> 100 2780 -0.00 0.1050 0.00</p><p> 125 2741 -0.26 0.1322 0.00</p><p> 150 2704 -0.82 0.1597 0.00</p><p> 175 2666 -1.67 0.1877 0.00</p><p> 200 2629 -2.82 0.2160 0.00</p><p> 225 2592 -4.29 0.2447 0.00</p><p> 250 2555 -6.09 0.2739 0.00</p><p> 275 2518 -8.21 0.3034 0.00</p><p> 300 2482 -10.68 0.3334 0.00</p><p> 325 2446 -13.50 0.3639 0.00</p><p> 350 2411 -16.68 0.3947 0.00</p><p> 375 2375 -20.24 0.4261 0.00</p><p> 400 2340 -24.18 0.4579 0.00</p><p> 425 2306 -28.52 0.4902 0.00</p><p> 450 2271 -33.27 0.5229 0.00</p><p> 475 2237 -38.44 0.5562 0.00</p><p> 500 2203 -44.04 0.5900 0.00</p><p> 525 2170 -50.09 0.6243 0.00</p><p> 550 2137 -56.60 0.6591 0.00</p><p> 575 2104 -63.59 0.6945 0.00</p><p> 600 2071 -71.07 0.7304 0.00</p><p> 625 2039 -79.05 0.7669 0.00</p><p> 650 2006 -87.56 0.8040 0.00</p><p> 675 1975 -96.60 0.8417 0.00</p><p> 700 1943 -106.21 0.8800 0.00</p><p> 725 1912 -116.38 0.9189 0.00</p><p> 750 1881 -127.16 0.9584 0.00</p><p> 775 1850 -138.54 0.9986 0.00</p><p> 800 1819 -150.57 1.0395 0.00</p><p> 825 1789 -163.24 1.0811 0.00</p><p> 850 1759 -176.60 1.1234 0.00</p><p> 875 1729 -190.66 1.1664 0.00</p><p> 900 1699 -205.45 1.2102 0.00</p><p> 925 1670 -220.98 1.2547 0.00</p><p> 950 1640 -237.30 1.3000 0.00</p><p> 975 1611 -254.43 1.3461 0.00</p><p> 1000 1583 -272.39 1.3931 0.00</p><p> 1025 1554 -291.22 1.4409 0.00</p><p> 1050 1526 -310.95 1.4896 0.00</p><p> 1075 1498 -331.61 1.5392 0.00</p><p> 1100 1470 -353.24 1.5898 0.00</p><p> 1125 1442 -375.87 1.6413 0.00</p><p> 1150 1415 -399.55 1.6938 0.00</p><p> 1175 1388 -424.32 1.7474 0.00</p><p> 1200 1361 -450.22 1.8019 0.00</p></blockquote><p></p>
[QUOTE="BryanLitz, post: 317788, member: 7848"] Bud, I think the problem may come from using the advertised G1 BC(s). I haven't measured the G7 BC for the 140 MK (I do have the 142 MK). Based on Sierra's advertised G1 BCs, this bullet should have a [B]G7 BC of 0.270*.[/B] I've generated the table below using that G7 BC and the following inputs; MV = 2935 fps I added 5 fps for velocity lost in the 10' from muzzle to target. This isn't a big deal considering there's probably more error than that in the Chrony. Temp = 59 deg F Pressure = 26.33 inHg (standard pressure at 3500 ft) Sight Height = 1.68" Zero range = 100 yards Note that the bullet path in the table is -375.87" at 1125 yards. That's equal to 31.9 MOA. You said you observed 31.2 MOA at that range, a difference of 0.7 MOA. You said your chart showed more drop; 33.4 MOA at that range. What BC did you use to generate that chart? How does the bullet path in the chart below compare to your records at other ranges? Range Velocity Trajectory TOF Drift (yards) (fps) (inches) (sec) (inches) 0 2935 -1.68 0.0000 0.00 25 2896 -0.86 0.0257 0.00 50 2857 -0.31 0.0518 0.00 75 2818 -0.02 0.0782 0.00 100 2780 -0.00 0.1050 0.00 125 2741 -0.26 0.1322 0.00 150 2704 -0.82 0.1597 0.00 175 2666 -1.67 0.1877 0.00 200 2629 -2.82 0.2160 0.00 225 2592 -4.29 0.2447 0.00 250 2555 -6.09 0.2739 0.00 275 2518 -8.21 0.3034 0.00 300 2482 -10.68 0.3334 0.00 325 2446 -13.50 0.3639 0.00 350 2411 -16.68 0.3947 0.00 375 2375 -20.24 0.4261 0.00 400 2340 -24.18 0.4579 0.00 425 2306 -28.52 0.4902 0.00 450 2271 -33.27 0.5229 0.00 475 2237 -38.44 0.5562 0.00 500 2203 -44.04 0.5900 0.00 525 2170 -50.09 0.6243 0.00 550 2137 -56.60 0.6591 0.00 575 2104 -63.59 0.6945 0.00 600 2071 -71.07 0.7304 0.00 625 2039 -79.05 0.7669 0.00 650 2006 -87.56 0.8040 0.00 675 1975 -96.60 0.8417 0.00 700 1943 -106.21 0.8800 0.00 725 1912 -116.38 0.9189 0.00 750 1881 -127.16 0.9584 0.00 775 1850 -138.54 0.9986 0.00 800 1819 -150.57 1.0395 0.00 825 1789 -163.24 1.0811 0.00 850 1759 -176.60 1.1234 0.00 875 1729 -190.66 1.1664 0.00 900 1699 -205.45 1.2102 0.00 925 1670 -220.98 1.2547 0.00 950 1640 -237.30 1.3000 0.00 975 1611 -254.43 1.3461 0.00 1000 1583 -272.39 1.3931 0.00 1025 1554 -291.22 1.4409 0.00 1050 1526 -310.95 1.4896 0.00 1075 1498 -331.61 1.5392 0.00 1100 1470 -353.24 1.5898 0.00 1125 1442 -375.87 1.6413 0.00 1150 1415 -399.55 1.6938 0.00 1175 1388 -424.32 1.7474 0.00 1200 1361 -450.22 1.8019 0.00 [/QUOTE]
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