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Leveling the Scope Reticle for Long Range Rifles

 
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  #43  
Old 03-06-2013, 01:32 AM
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DocB,

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Are you saying the scope is rotated counterclockwise 2 degrees or the base is angled off center 2 degrees?
- The scope is rotated counterclockwise relative to true horizontal. In practice, the anti-cant indicator is rotated clockwise.

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After you dial up to 1000yds, are you still shooting the same POA on the same 100yd target as the first group you fired?
- Yes, the impacts will land far above the first group.
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  #44  
Old 03-06-2013, 07:15 AM
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Re: Leveling the Scope Reticle for Long Range Rifles

Yes , the scope itself is canted left( counterclockwise) and with the scope in that position, the level is installed reading level. It is about a half a bubble off plumb! This can be done in the shop with a gun or scope vice and a vertical line about 25 yards away(far enough to get a focused image with the scope. Make a vertical line with a carpenters level. Now, I calculate the value of 2.5 degrees at a height of 24 inches. At this height, one degree is about .42 inches so 2.5 degrees is about one inch.( formula pii X diameter in inches divided by 360 degrees) Now, from a point, on the line measure up 24 inches and left 1 inch and connect the two points. Now, with the scope/gun in a vice, allign the scope with the canted line and install the level on the scope. The scope is tilted 2.5 degrees and the level stays level. It would be easier if the level screws were on the top instead of the bottom! The next step is getting the gun held in a comfortable position and then rotating the scope and level untill the horizontal is affirmed by the level. This is a custom set up for those that find it difficult to keep the gun from canting as indicated by the level. Most guns I do are level and square and the shooter must make those adjustments as he sees fit. Some don't want to pay that extra $50.00 for a level but it will make all the difference in the world! One word about spin drift, with the 2.5 degrees cant, on the 100 yard target, 1000 yards of elevation is 23 moa and 1500 yards is 51 moa so it is allowing almost 30 inches for spin drift at 1500 yards while only 10 inches at 1000. It is hard to get completly calm conditions to test, but to the best of my ability, this seems to work. another thing to remember is that after 1000 yards, everything goes south and all varibles are greatly increased and Coriolis must be allowed for. Hope this helps!
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  #45  
Old 03-06-2013, 09:43 AM
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Re: Leveling the Scope Reticle for Long Range Rifles

Another thought here, don't get discouraged reading all of this stuff! First, learn good skills at short ranges with small guns. Shoot enough , practice enough, to know if a gun shoots well and also to know if YOU shoot well! As you gain experience, all these other things will fall in place. Long range is a great sport and it is great to have guys like Bruce to help define the science of ballistics. Play with a smallbore and scope to see what happens when you try these ideas promoted in this thread and other great threads on this forum. And, most of all, don't believe everything you read! Think things through before doing things that could be dangerous! Have fun shooting!
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  #46  
Old 03-06-2013, 01:10 PM
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Re: Leveling the Scope Reticle for Long Range Rifles

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Originally Posted by paphil View Post
Another thought here, don't get discouraged reading all of this stuff! First, learn good skills at short ranges with small guns. Shoot enough , practice enough, to know if a gun shoots well and also to know if YOU shoot well! As you gain experience, all these other things will fall in place. Long range is a great sport and it is great to have guys like Bruce to help define the science of ballistics. Play with a smallbore and scope to see what happens when you try these ideas promoted in this thread and other great threads on this forum. And, most of all, don't believe everything you read! Think things through before doing things that could be dangerous! Have fun shooting!
I asked earlier and am still curious, why do we use 'right hand' barrels in the northern hemisphere instead of 'left handed' ones?

Doc
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  #47  
Old 03-06-2013, 03:56 PM
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Re: Leveling the Scope Reticle for Long Range Rifles

I don't know of any barrel makers that make left twist but I've heard of some European guns that have Left twists. The problem is the same only in the opposite direction. Spin drift is not the same in all bullets and calibers but as best as I can tell, it is between 6 and 12 inches at 1000 yards depending on the twist speed and the shape of the bullet. Coriolis is an addition to or subtracted from the spin drift depending on direction of flight of the bullet and the time of flight. Shooting east will cause the bullet to hit high because the earth and the target are falling. about 3 inches at 1000 yards with a 7mm vld. shooting west is just the opposite . The earth and the target are rising and the bullet will hit low, again about 3 inches. Shooting north and south is still a question in my mind, but if the target is moving with the earth, it would move left to right looking north and right to left shooting south. Still about 3 inches for a 7mm vld with mv of 3000 fps. All of this is very hard to prove due to other environmental issues but I'm sure there is a mathmatical solution. This is all based on time of flight so slower bullets and longer shots will have more effect. Maybe there is someone with artillary backround that could post their thoughts! Not many guns shoot well enough to tell these small effects but when you add them all togather it makes those shooter programs look pretty handy.
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  #48  
Old 03-06-2013, 04:14 PM
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Re: Leveling the Scope Reticle for Long Range Rifles

Spin and Coriolis Drift
this is a good link by Brian Litz
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  #49  
Old 03-06-2013, 06:14 PM
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Re: Leveling the Scope Reticle for Long Range Rifles

Quote:
Originally Posted by paphil View Post
Another thought here, don't get discouraged reading all of this stuff! First, learn good skills at short ranges with small guns. Shoot enough , practice enough, to know if a gun shoots well and also to know if YOU shoot well! As you gain experience, all these other things will fall in place. Long range is a great sport and it is great to have guys like Bruce to help define the science of ballistics. Play with a smallbore and scope to see what happens when you try these ideas promoted in this thread and other great threads on this forum. And, most of all, don't believe everything you read! Think things through before doing things that could be dangerous! Have fun shooting!

So far, this has been the most reasonable advice offered.

Remember, it remains very difficult to replicate decades of experience within 5-10 paragraphs of written instructions.
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