How important or close do you need to be for center of scope to center of bore?

Trees91

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Oct 27, 2018
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Making up ballistic charts and wondering how perfect this measurement needs to be or what is the best way to measure?
 

TNKnoxville

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Knoxville, TN
I opened my bolt and pulled it back until I could get a good position to set the ruler against the center of the bolt and the middle of the scope. Was able to easily get to within a 1/10". Does that make sense??
 

Wrench

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WA
I measure diameter of action ÷2 plus space between action and bottom of tube @ erector adjustment, plus 50% of scope tube diameter......then fire to validate.
 

BCD

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Hudson, WI
I saw a youtube video on this and if I recall correctly being off by 1/10 of an inch on the measurement equated to less than 3/4 inch at 1000 yards.
 
OP
Trees91

Trees91

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South Dakota
Thats encouraging. I’ll just pull the bolt back till it’s flush with the ocular end of the scope and measure with calipers. I think it’ll be close enough.
 

Stalker69

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Apr 12, 2019
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So just a thought, he measures from the back of the bolt to center of scope. Does having a 20 moa base on it change the measurement ? As the front of the scope is going to be different then the back of the scope ?
 

ChrisAU

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Its pretty simple, use a caliper, harbor freight has them super cheap.

1/2 of bolt diameter + 1/2 of scope tube diameter + distance between bottom of scope tube and top of bolt = sight height.
 

BCD

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Jan 9, 2019
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Hudson, WI
So just a thought, he measures from the back of the bolt to center of scope. Does having a 20 moa base on it change the measurement ? As the front of the scope is going to be different then the back of the scope ?

He mentions this in the video (or maybe it was a different one with him in it) that you don't need to account for the 20 MOA rail.
 
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