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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
Leveling your scope
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<blockquote data-quote="MontanaRifleman" data-source="post: 256728" data-attributes="member: 11717"><p>JWP, do you have a ref for David Tubb's shooting canted. It's not that I dont believe you, but I would just like to read it to get it in context with no misunderstanding.</p><p> </p><p>Mike, I still dont think I understand you, if you agiln your scope to the sdie of your bore (bullet path) you are going to induce downrange error. Also, it matters little if you are using crosshairs or dots. The dots are alinged along verticle and horizontal planes and are adjusted vertically(elevation) and horizontally(windage).</p><p> </p><p>OK guys, we live in a world with certain mathematical and geometric principles as we as physical laws that include force, mass, gravity, friction, etc. And what I think I have been reading from some defies those principles and laws. and being the self appointed policeman, I am here to bust you and hand out citations</p><p> </p><p>Let's make an exagerated example to illustrate.</p><p> </p><p>Lets take a scoped rifle, with scope and reticle aligned vertically with the rifles bore. The center of scope rests 1.5" above the center of bore. The bullet has a BC of .3, MV of 3000 fps and zero'd in at 25 yds, at sea level. The definition of zero is the point were the bullet path meets the sight path of the scope (crosshair or dot). We will all agree that the sight path is a straightline and the bullet path is an arc'd line (which can defined by a plain) If we "aim" the scope straight ahead at the horizon, we must aim the bore in the same forward direction but slightly upward above the horizon to achieve the zero point. We also agree that the bullet will crest and begin to dip below the horizon at some point and in a no wind situation will intersect again with the scopes sight path, which in this case is exactly 250 yds down range.</p><p> </p><p>OK then... now let's cant the rifle completely over on its side, 90* in a no gravity situation. If we aim and fire at our target, 25 yds away, what hapens? Correct, we hit the bulyseye or very close. If we aim and fire at our second zero, 250 yds away, what happens? The bullet impacts 13 1/2 inches to the side of the POA (second zero point). If we add gravity the bullet still impacts 13 1/2 inches o the side of POA but it also drops, approx 8-9 inches. </p><p> </p><p>OK... Let's only cant the rifle 45*. The results are similar but the bullet doesn't drift quite as far to the side (approx 10 inches) nor drop as much. Actually it does drop as much, but since it is point "up" and not "straight ahaed", the drop doesn't *appear* to be as much. The farther we cant our rifle back to verticle the closer our bullet gets to POA. This not my opinon or theory. This is mathematic and geometric, physical fact. </p><p> </p><p>If you always cant your rifle to the same tilt and shoot at the same zero point and distance you will always hit your POA if you zero'd in that configuration. if you shoot at different distances with a canted rifle and scope your buleit WILL drift. That is a mathematical fact.</p><p> </p><p>If your reticle is not plumbed to gravity (what else would it be plmbed to?) And you dial in elevation correction, your correction will cause your POI to shift, if you use the same POA. That is not an opinion, that's a cold hard fact.</p><p> </p><p>If any of you can prove otherwise on the range, I sure would be interested, because all the geometry, trigonomitry and physics books will have to be rewritten. So please do experiment. Take your rifle and cant it 45* and shoot at a target 250 or 300 yds away, and cant it again at 30*, 10* and verticle and see what happens.</p></blockquote><p></p>
[QUOTE="MontanaRifleman, post: 256728, member: 11717"] JWP, do you have a ref for David Tubb's shooting canted. It's not that I dont believe you, but I would just like to read it to get it in context with no misunderstanding. Mike, I still dont think I understand you, if you agiln your scope to the sdie of your bore (bullet path) you are going to induce downrange error. Also, it matters little if you are using crosshairs or dots. The dots are alinged along verticle and horizontal planes and are adjusted vertically(elevation) and horizontally(windage). OK guys, we live in a world with certain mathematical and geometric principles as we as physical laws that include force, mass, gravity, friction, etc. And what I think I have been reading from some defies those principles and laws. and being the self appointed policeman, I am here to bust you and hand out citations Let's make an exagerated example to illustrate. Lets take a scoped rifle, with scope and reticle aligned vertically with the rifles bore. The center of scope rests 1.5" above the center of bore. The bullet has a BC of .3, MV of 3000 fps and zero'd in at 25 yds, at sea level. The definition of zero is the point were the bullet path meets the sight path of the scope (crosshair or dot). We will all agree that the sight path is a straightline and the bullet path is an arc'd line (which can defined by a plain) If we "aim" the scope straight ahead at the horizon, we must aim the bore in the same forward direction but slightly upward above the horizon to achieve the zero point. We also agree that the bullet will crest and begin to dip below the horizon at some point and in a no wind situation will intersect again with the scopes sight path, which in this case is exactly 250 yds down range. OK then... now let's cant the rifle completely over on its side, 90* in a no gravity situation. If we aim and fire at our target, 25 yds away, what hapens? Correct, we hit the bulyseye or very close. If we aim and fire at our second zero, 250 yds away, what happens? The bullet impacts 13 1/2 inches to the side of the POA (second zero point). If we add gravity the bullet still impacts 13 1/2 inches o the side of POA but it also drops, approx 8-9 inches. OK... Let's only cant the rifle 45*. The results are similar but the bullet doesn't drift quite as far to the side (approx 10 inches) nor drop as much. Actually it does drop as much, but since it is point "up" and not "straight ahaed", the drop doesn't *appear* to be as much. The farther we cant our rifle back to verticle the closer our bullet gets to POA. This not my opinon or theory. This is mathematic and geometric, physical fact. If you always cant your rifle to the same tilt and shoot at the same zero point and distance you will always hit your POA if you zero'd in that configuration. if you shoot at different distances with a canted rifle and scope your buleit WILL drift. That is a mathematical fact. If your reticle is not plumbed to gravity (what else would it be plmbed to?) And you dial in elevation correction, your correction will cause your POI to shift, if you use the same POA. That is not an opinion, that's a cold hard fact. If any of you can prove otherwise on the range, I sure would be interested, because all the geometry, trigonomitry and physics books will have to be rewritten. So please do experiment. Take your rifle and cant it 45* and shoot at a target 250 or 300 yds away, and cant it again at 30*, 10* and verticle and see what happens. [/QUOTE]
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