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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
calculations 2moa off, need advice
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<blockquote data-quote="LouBoyd" data-source="post: 398802" data-attributes="member: 9253"><p>Goose, I agree with what others have posted. But I didn't see where anyone asked if you'd measured the distance between the centerline of your bore and the centerline of the scope accurately and entered that distance into your ballistics program. All ballistics programs I've seen have a place for that and it's important. Having that entry wrong by about two inches would account for the 2 MOA error with a 100 yard zero when shooting at 400 yards and beyond. If you set it better than about 0.1" the error won't be noticeable . </p><p></p><p>There are other possibilities which could be causing a 2 MOA error but that one is easily missed by new users of ballistics programs.. Been there, done that. Wrong muzzle velocity, air density, and bullet BC are also possible errors but less likely in my opinion. Two MOA is a lot. The scope or rifle having a problem is very unlikely. </p><p></p><p>If you're serious about ballistic calculations do get a range finder and a chronograph. For hundreds of years shooters were reasonably successful with neither. That came from lots of practice, some in estimating distance and holdover but mostly from learning to stalk close the their targets.</p><p></p><p>Google Earth can be used for distance measurements with an accurate of a couple of yards at reasonable shooting distanced (further than most range finders) but only IF you can identify objects on the ground. The photos can be ten years old or more. Google earth has a built in tool for measuring straight lines between points. I'm not sure if if gives the slope distance or the map projected distance but it does not give the slope angle. One possible advantage over a range finder is it can give the distance even though a hill (for those high trajectory shots).</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 398802, member: 9253"] Goose, I agree with what others have posted. But I didn't see where anyone asked if you'd measured the distance between the centerline of your bore and the centerline of the scope accurately and entered that distance into your ballistics program. All ballistics programs I've seen have a place for that and it's important. Having that entry wrong by about two inches would account for the 2 MOA error with a 100 yard zero when shooting at 400 yards and beyond. If you set it better than about 0.1" the error won't be noticeable . There are other possibilities which could be causing a 2 MOA error but that one is easily missed by new users of ballistics programs.. Been there, done that. Wrong muzzle velocity, air density, and bullet BC are also possible errors but less likely in my opinion. Two MOA is a lot. The scope or rifle having a problem is very unlikely. If you're serious about ballistic calculations do get a range finder and a chronograph. For hundreds of years shooters were reasonably successful with neither. That came from lots of practice, some in estimating distance and holdover but mostly from learning to stalk close the their targets. Google Earth can be used for distance measurements with an accurate of a couple of yards at reasonable shooting distanced (further than most range finders) but only IF you can identify objects on the ground. The photos can be ten years old or more. Google earth has a built in tool for measuring straight lines between points. I'm not sure if if gives the slope distance or the map projected distance but it does not give the slope angle. One possible advantage over a range finder is it can give the distance even though a hill (for those high trajectory shots). [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
calculations 2moa off, need advice
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