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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Oct 1, 2018
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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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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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Jan 12, 2018
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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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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.
 

davsco

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Jan 30, 2018
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VA
see for yourself how precise the measurement has to be. take your measurement from center of scope to center of bolt. plug that in. see what your hold is at the furthest distance you will be shooting. than add 1/8 inch to that measurement and see what your hold is. then subtract 1/8 inch.
 

bruceleroy

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Dec 29, 2015
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I've never changed whatever number my Strelok had for height.
I just ran my numbers and the difference between scope over bore height of 1.25, 1.5 (what was already in my app), and 1.8 at 1k yards was .25 MOA.
I wont be stressing about this...still.
 

DB Cooper

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Nov 13, 2017
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Klamath Falls, OR
Its insignificant compared to making sure your gun is zeroed at the distance you think it is. Example: Thinking you are zeroed with a 300 WM at 100 yds when you're actually zeroed in at 200 yds will be a 1.25 MOA error at 400 yds, a 1.5 MOA at 500 yds, and a 1.75 MOA error at 600 yds

I know this because I screwed up the calc. at the range monday
 
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