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Left @ 300 yds - Right @ 1000 yds? WTH?

 
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  #8  
Old 11-02-2008, 10:28 PM
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Join Date: Dec 2007
Location: sebastopol, ca.
Posts: 418
Re: Left @ 300 yds - Right @ 1000 yds? WTH?

The scope reticle is very rarely EXACTLY plumb with the flat on the bottom of the scope or the the turret caps.

It must be exact for serious long range. Once you get the scope plumb use your power pole technique to get your rifle level and put a bubble level on your scope.

There are several made that work really well. I bought mine for my 300 win mag from Shawn at Defensive Edge. Great guy with great service. Look at the cosine indicator if you shoot in the mountains and you can mount the level and the indicator on the same mount.

Spin drift only applies to really long range from what I know about it. It was used for long range artillery calculations. Comes into play when you are shooting miles instead of yards.

The scope level thread is very interesting I printed it and have read it several times.

Good luck and let us know how you do.
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  #9  
Old 11-02-2008, 10:40 PM
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Join Date: Oct 2005
Location: Michigan
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Re: Left @ 300 yds - Right @ 1000 yds? WTH?

Phorwath,


OK, bullet moving left to right?
Maybe it's compensating for your recent right to left political leanings? ;)


In all seriousness though, the guys have given you all the likely causes.


Good luck,
AJ
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  #10  
Old 11-02-2008, 10:55 PM
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Join Date: May 2007
Location: California
Posts: 458
Re: Left @ 300 yds - Right @ 1000 yds? WTH?

Maybe the base or the mounting srew holes are misaligned right to left relative to the bore.

Sounds similar to the problem encountered in shooting a side-mounted rifle scope (like on a M1 sniper rifle), but to a much lesser degree.

Last edited by LewisH; 11-03-2008 at 01:48 AM.
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  #11  
Old 11-02-2008, 11:07 PM
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Join Date: Apr 2005
Location: Alaska
Posts: 3,389
Re: Left @ 300 yds - Right @ 1000 yds? WTH?

Quote:
Originally Posted by AJ Peacock View Post
Phorwath,


OK, bullet moving left to right?
Maybe it's compensating for your recent right to left political leanings? ;)


In all seriousness though, the guys have given you all the likely causes.


Good luck,
AJ
Ha!!! I appreciate a good sense of humor! Caught me with my pants down on this one.
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  #12  
Old 11-02-2008, 11:11 PM
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Join Date: Apr 2005
Location: Alaska
Posts: 3,389
Re: Left @ 300 yds - Right @ 1000 yds? WTH?

Well if spin drift or some other kind of voodoo doesn't explain this then I'll work to ensure my scopes are both mounted in proper alignment with the bore. They reticles look straight with the gun and world, but maybe they're just a tad catty wompus. I'll let you know if/when I get to the bottom of this puzzler. Thanks.
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  #13  
Old 11-03-2008, 03:52 AM
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Join Date: Apr 2005
Location: Alaska
Posts: 3,389
Re: Left @ 300 yds - Right @ 1000 yds? WTH?

OK guys,

kiwi3006 provided a link to a LRH thread, which contained a link to this thread at the Sniper's Hide. Thanks kiwi.

Spindrift Calculation?? - Sniper's Hide Forums

Now I don't advise anyone to read that whole thread unless you're really into this stuff. It's a very, very long thread and it took me about 2-3 hours of time to digest the entire thread. Summarizing, the jist of it is that spindrift is for real, and with my rifles and bullets, I could expect to see about 10" (~1 moa) of left-to-right spindrift (based on right hand twist rifling) at 1000 yds. So spindrift could indeed explain most of the left-to-right drift I'm experiencing with my 300 Win Mag.

Spindrift doesn't account for the excessive left-to-right drift I'm experiencing with the 7mm Rem Mag. I'm getting about twice the drift attributed to spindrift with this setup. So I'm going to take a good close look at the scope set-up on my 7mm and make sure I haven't mounted the scope with a slight counter-clockwise rotation from vertical. If the scope were canted counterclockwise, then when I leveled the crosshairs, the bore would send the bullet downrange with a slight right drift. That's currently my best explanation.

Any other thoughts, I'm all ears. Other than that, I'll let you know how this pans out.
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  #14  
Old 11-04-2008, 09:46 AM
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Join Date: Nov 2008
Location: Olympia,Washington
Posts: 25
Re: Left @ 300 yds - Right @ 1000 yds? WTH?

I don't know what bases you are using, solid or windage adjustable, but I had the same problem with my 300Win mag Leupold 4.5 x14LR with Leupold windage adjustable bases. If your scope is not in perfect alignment with your barrell for windage you will experience crossover. A lot of shooters, and shops for that matter, will mount a scope on windage adjustable bases, then adjust the windage using only the crosshair windage adjustment. It is very important to adjust the windage first by using the windage adjustment on the base, fine tune with the crosshair adjustment. It is very important to start with the crosshairs centered for windage. A very easy way to check this is to place a mirror against the objective of your scope, if you see two sets of windage crosshairs, the crosshairs are not centered. Bring the crosshairs back to zero and adjust windage first by adjusting the base adjustment. Hope this helps, it solved my problems
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