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#3313526 - 02/06/23 10:35 PM Thermal Scope Mounting Trivia
topwater225 Offline
Junior Member

Registered: 12/16/07
Posts: 45
Loc: Utah
A little trivia question for you all about my thermal scope mounting:
My rifle has a 20 MOA rail. I have a Bobro mount that Iíve used for a couple of years. I previously was using an Iray Bolt scope, and zeroing it didnít take much adjustment. For reference my elevation had to go up to around 23.5 to be zeroed.

Fast forward: I now have a Thermion. I went out to zero it and it was WAY high. I ended up needing to move the reticle up to 98.50! Everything seems to be mounted in the same locations (on the scope and on the base).

I can live with the reticle being so far up on the screen display, but it does bug me. So Iím going to try to move my Bobro mount further back on the 20 MOA base to essentially raise my reticle lowering my poi.

The question is why do you think there is such a discrepancy on the two scopes? Is my theory correct in adjusting the Bobro mount further back on the base?


Edited by topwater225 (02/07/23 01:09 PM)

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#3313534 - 02/06/23 11:15 PM Re: Thermal Scope Mounting Trivia [Re: topwater225]
spotstalkshoot Online
Die Hard Member III

Registered: 12/22/13
Posts: 2643
Loc: so.mn
No, I think you need a flat (0 moa) rail.

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#3313573 - 02/07/23 11:24 AM Re: Thermal Scope Mounting Trivia [Re: topwater225]
alf Offline
Die Hard Member II

Registered: 03/25/07
Posts: 1929
Loc: SW Wisconsin
Originally Posted By: topwater225
So Iím going to try to move my Bobro mount further back on the 20 MOA base to essentially raise my reticle lowering my poi.
Is my theory correct in adjusting the Bobro mount further back on the base?

I'm not a mathematics professor, but I'm pretty sure it won't make any difference, 20 MOA is 20 MOA no matter it's position on the rail.

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#3313587 - 02/07/23 12:07 PM Re: Thermal Scope Mounting Trivia [Re: alf]
spotstalkshoot Online
Die Hard Member III

Registered: 12/22/13
Posts: 2643
Loc: so.mn
MOA value will change with ring SPACING(distance between ring centers) on the rail.


Edited by spotstalkshoot (02/07/23 12:09 PM)

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#3313592 - 02/07/23 01:08 PM Re: Thermal Scope Mounting Trivia [Re: spotstalkshoot]
topwater225 Offline
Junior Member

Registered: 12/16/07
Posts: 45
Loc: Utah
This is what I'm thinking....

The rail is canted (higher in the back and narrows forward. So I would think placement of the mount would make a difference in the reticle position.

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#3313595 - 02/07/23 02:01 PM Re: Thermal Scope Mounting Trivia [Re: spotstalkshoot]
alf Offline
Die Hard Member II

Registered: 03/25/07
Posts: 1929
Loc: SW Wisconsin
Originally Posted By: spotstalkshoot
MOA value will change with ring SPACING(distance between ring centers) on the rail.

True, but not applicable in this situation, as the scope is already mounted.

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#3313600 - 02/07/23 03:23 PM Re: Thermal Scope Mounting Trivia [Re: alf]
spotstalkshoot Online
Die Hard Member III

Registered: 12/22/13
Posts: 2643
Loc: so.mn
Yes scope is mounted to a QD base, mounted on a 20 moa rail, get a 0 moa rail. Get the sight display perpendicular to the barrel and rail.

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