OK Trig majors, MOA question about scope shims

Canuck223

Canuck223

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Can anyone tell me how many MOA I'm moving my scope rail by shimming the rear upwords .040? The distance between the front and rear mount screw is 8.5 inches.

It's on my Rhineland Arms R22. I've installed a .040 washer under the rear mount screw. I'm using a Holosight, and I've run out of verticle adjustment with the POI still one inch low at 20 yards. I'm hoping this shim will give me a few inches of adjustment.
 
Here's the math for a distance of 100 yds:

100 yds = 300ft = 3600 inches

If the distance between the front and rear mounts is 8.5 inches, then the distance to the target is 423.52 times (3600 divided by 8.5) greater than the distance between the mounts.

Therefore, raising the rear base .040 inches higher than the front base will change the line of sight .040 inches X 423.52 = 16.94, say 17 inches at 100 yds.

This will be the same for each increment of 100 yds, or portion thereof. For example, at 300 yds it will be 51 inches, 1000 yds would be 170 inches.

Remember this is line of sight, which is straight, not bullet path, which is parabolic.

Ted
 
Last edited:
Canuck223 said:
You da man Ted!!! If correct, that should put my scope back into the range I need.
Click to expand...

Canuck223,

I just realized you were concerned about the effect at 20 yds.

The line of sight at that distance will be changed by 20/100 X 17 = 3.4 inches. :cool:

Ted
 
I tested it today, and while it's still pegged at the upper limit of travel, at least my POI is in the black!!!
 
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