Amount of cant for scope

Medium Caliber, Bolt Action Precision Rifle

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bobk538447
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Amount of cant for scope

Postby bobk538447 » Wed 08 Jun, 2011 12:59 pm

What amount of cant will I need to maximize my 98B to it's fullest based upon a Leupold MK 4 6.5x20x50 ER/T M1 that according to the specs has 70 MOA internal adjustments. Thanks!
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Shadow
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Re: Amount of cant for scope

Postby Shadow » Wed 08 Jun, 2011 3:44 pm

bobk538447 wrote:What amount of cant will I need to maximize my 98B to it's fullest based upon a Leupold MK 4 6.5x20x50 ER/T M1 that according to the specs has 70 MOA internal adjustments. Thanks!


Precise answer would be dependent on the ammo you plan to shoot, the measured MV of the round and the BC, plus your environmentals. But that is not helpful without having the rifle set up to shoot, etc. I'd say any rifle is mazimized, if it'll provide scope adjustments out to the range where the bullet goes subsonic. So....

A General answer - With a 20MOA rail, you should be able to reach out to 1700 yds. I wouldn't get anything greater than a 20MOA rail (or rings). I can't imagine shooting anything beyond 1200yds with a .338LM, but that's just me. Beyond 1200yds, I personally move over to the .50BMG.

Anyway..as an example...
I often shoot .338LM - Scenar 250g HPBT with a MV of around 2960. The round goes subsonic at about 1850yds. It'll take about 68MOA to reach out to 1850yds and about 58MOA to get out to 1700yds.

With a 20MOA rail, you should be able to get elevation adjustments out to about 1700yds and still be able to adjust for very close ranges, but your mileage may vary. I'm certain other .338LM shooters will have experiences to share.

Good Luck.
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bobk538447
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Re: Amount of cant for scope

Postby bobk538447 » Wed 08 Jun, 2011 7:06 pm

Thank you Shadow!
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Re: Amount of cant for scope

Postby Dsully » Thu 09 Jun, 2011 5:06 am

Shadow is pretty good in the information department :)
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Re: Amount of cant for scope

Postby Kiwi Greg » Sun 12 Jun, 2011 2:38 pm

Get some Barrett X-rings 15-40 & move them further apart to support the scope better & also to give you more options.
Thats what I put on my 98B, very happy with them :cheer:
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Re: Amount of cant for scope

Postby Dsully » Mon 13 Jun, 2011 9:48 am

Kiwi Greg wrote:Get some Barrett X-rings 15-40 & move them further apart to support the scope better & also to give you more options.
Thats what I put on my 98B, very happy with them :cheer:


The directions say there is a specific amount of space needed for those rings. Make sure to follow the instructions
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Re: Amount of cant for scope

Postby Kiwi Greg » Tue 14 Jun, 2011 2:35 pm

Dsully wrote:
Kiwi Greg wrote:Get some Barrett X-rings 15-40 & move them further apart to support the scope better & also to give you more options.
Thats what I put on my 98B, very happy with them :cheer:


The directions say there is a specific amount of space needed for those rings. Make sure to follow the instructions


Moving them further apart will support the scope better but reduce elevation available, so if you adjust the rings to 40 moa & move them apart you still should have over 30 moa available :cool:
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Re: Amount of cant for scope

Postby bobk538447 » Tue 14 Jun, 2011 7:11 pm

I appreciate the feedback.
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Re: Amount of cant for scope

Postby cdparker » Mon 20 Jan, 2014 4:11 am

Is there a standard distance between the X rings? What I did with my gun was to mount my scope in the rings. Turn the elevation knob down until it bottomed out, come up 1 mil. with the x rings a wee loose, bore site at 100 yds. Lock rings and shoot. I moved the rings until I was very close, maybe a bit low and locked the rings again. Then I finished my sight-in and zeroed my knobs. This way, I have about all the elevation in my scope to go up. Right? At 100 yards, both the 250 and the 300 gr. strike very close to each other so I can compute "come ups" from there.
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Re: Amount of cant for scope

Postby shotgun » Mon 20 Jan, 2014 2:19 pm

They also make the EX rings in 20/30moa. I could never see needing 40moa on top of a already canted rail. I don't think you could ever get a zero below400+ yds(depending on the scope and if you had a low power/high elevation range you would not need the 40moa in the first place) and 10moa might not be enough for higher magnification scopes low adjustment range i.e.-NF 12-42x56 with only 45moa of total elevation adjustment. So-- 30moa(rifles rail)+22.5moa(scopes upward travel from mid point)+ 20moa(ex-rings low position)=72.5moa of "up" adjustment, plenty to reach out beyond a mile in Shadow's example. Plus you have an extra 10moa by pinning the EX-rings in the 30moa position if you ever need it. This is a close approximation, as stacking 2 angles on top of each other requires a trig solution to get it exact. You are just angling the scope downward and once you get to the bottom of your scopes total elevation travel you then are increasing the range at which it will close zero. Your scope has 90moa total elevation? If so, you could add another 22.5moa to your upward "clicks" and have a much closer "close" zero to the above example. :cheer:
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Re: Amount of cant for scope

Postby shotgun » Mon 20 Jan, 2014 2:40 pm

cdparker wrote:Is there a standard distance between the X rings? What I did with my gun was to mount my scope in the rings. Turn the elevation knob down until it bottomed out, come up 1 mil. with the x rings a wee loose, bore site at 100 yds. Lock rings and shoot. I moved the rings until I was very close, maybe a bit low and locked the rings again. Then I finished my sight-in and zeroed my knobs. This way, I have about all the elevation in my scope to go up. Right? At 100 yards, both the 250 and the 300 gr. strike very close to each other so I can compute "come ups" from there.

Just be sure to loosen the pivot screws on the front ring so it does not bind. changing the distance between the rings changes the angle of the mounting surface area, and it could damage your scope and/or the rings. 100 yds is a perfect starting point as long as your scope has enough adjustment range to reach out to the distance you want to shoot.
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