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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
You Only Need to Know This If You Shoot Past 700 Yards!
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<blockquote data-quote="LouBoyd" data-source="post: 765566" data-attributes="member: 9253"><p>If you want the most accurate results arguably you shoudn't be using BC's at all. For most low drag bullets the G7 is better than G1, but there are still significant differences between the predictions and reality. Look at Brian Litz's book in the back chapters where the match between G1 and G7 trajectories are compared to millimeter radar measurements of the actual velocity vs air density results. In most cases the G7 is a better match for "long range" bullets. There are some notable examples where the G1 is a better match. The 240 grain Sierra Matchking is an example. It's really not a VLD design even though it's a spitzer boatail. </p><p></p><p>Most of us don't have access to a range equipped with mm doppler radar and I don't know of any available ballistics programs which allow entering doppler radar results directly even if you have them. </p><p></p><p>You do have the option of doing your own shooting tests from your rifle and cartridges. It's more tedious than just relying on a computer output but you can use most modern ballistics programs to "curve fit" measured results to give better results than you're likely to get using manufacturers published G1 or G7 numbers. By better results I mean a better prediction of shot placement at various ranges using your handloads (or specific model of quality factory ammo). and your rifle in your environment. You still have to adjust for your local air density at the time you shoot and (perhaps) the temperature of your ammo at the time of firing. </p><p></p><p>Few shooters want to take the time and effort to get the most accurate results for "first shot" accuracy. For target shooter who are allowed sighters knowing the exact BC and exact air density makes little difference. For hunters, snipers, and some competition with targets requiring first shot hits at random targets and random ranges it may be worth the effort. </p><p></p><p>I have far more confidence in a set of range cards set up for my rifle and specific ammo for a range of air density derived from shooting tests made in the environment where I shoot than any computer generated results based on factory numbers for BC. You can make a good table over the supersonic range of a rifle with about 20 carefully fired shots. Certainly using G() functions and a ballistic calculator are useful just to put the shots on a target face so you can measure them. Wind deflection can be calculated from accurate drop measurements. Trying to measure wind deflection vs natural wind vectors in taking the drop measurements for the range card. Shooting over flat land in low wind will result in better quality drop measurements.</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 765566, member: 9253"] If you want the most accurate results arguably you shoudn't be using BC's at all. For most low drag bullets the G7 is better than G1, but there are still significant differences between the predictions and reality. Look at Brian Litz's book in the back chapters where the match between G1 and G7 trajectories are compared to millimeter radar measurements of the actual velocity vs air density results. In most cases the G7 is a better match for "long range" bullets. There are some notable examples where the G1 is a better match. The 240 grain Sierra Matchking is an example. It's really not a VLD design even though it's a spitzer boatail. Most of us don't have access to a range equipped with mm doppler radar and I don't know of any available ballistics programs which allow entering doppler radar results directly even if you have them. You do have the option of doing your own shooting tests from your rifle and cartridges. It's more tedious than just relying on a computer output but you can use most modern ballistics programs to "curve fit" measured results to give better results than you're likely to get using manufacturers published G1 or G7 numbers. By better results I mean a better prediction of shot placement at various ranges using your handloads (or specific model of quality factory ammo). and your rifle in your environment. You still have to adjust for your local air density at the time you shoot and (perhaps) the temperature of your ammo at the time of firing. Few shooters want to take the time and effort to get the most accurate results for "first shot" accuracy. For target shooter who are allowed sighters knowing the exact BC and exact air density makes little difference. For hunters, snipers, and some competition with targets requiring first shot hits at random targets and random ranges it may be worth the effort. I have far more confidence in a set of range cards set up for my rifle and specific ammo for a range of air density derived from shooting tests made in the environment where I shoot than any computer generated results based on factory numbers for BC. You can make a good table over the supersonic range of a rifle with about 20 carefully fired shots. Certainly using G() functions and a ballistic calculator are useful just to put the shots on a target face so you can measure them. Wind deflection can be calculated from accurate drop measurements. Trying to measure wind deflection vs natural wind vectors in taking the drop measurements for the range card. Shooting over flat land in low wind will result in better quality drop measurements. [/QUOTE]
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You Only Need to Know This If You Shoot Past 700 Yards!
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