# center of scope to bore exbal question

#### lamiglas

##### Well-Known Member
What i am doing now seems to work, but a friend and I are doing this a little different so i wanted to hear how you all are doing this. do you measure the distance from center of bore to center of scope to input into exbal from:

1) near the bolt, or

2) at the front of the scope

with a slanted base the two measurements would be slightly different ( i am thinking) but please correct if wrong.

thanks alot guys.

#### geargrinder

##### Well-Known Member
I measure the distance between the bottom of the scope and the top of the bolt. Then I add half the diameter of the scope tube and half the diameter of the bolt.

#### Southpaw

##### Well-Known Member
What I was always told, and what I do is use the middle of the bolt. I measure just in front or behind the turrets, which ever is closest.

Works for me.

Southpaw

#### morpheus32

##### Member
I take a slightly different approach when looking at the height of the scope above the barrel.

From the objective end, I measure the scope complete. I then measure the gap between the bottom of the scope and the top of the barrel. I thing measure the barrel just below the objective end. Add all three and divide by two. It works well for me and is vary accurate as I can use my calipers to measure each. I would suggest this method takes out some of the guessing on the centre.

#### Moman

##### Well-Known Member
I take a slightly different approach when looking at the height of the scope above the barrel.

From the objective end, I measure the scope complete. I then measure the gap between the bottom of the scope and the top of the barrel. I thing measure the barrel just below the objective end. Add all three and divide by two. It works well for me and is vary accurate as I can use my calipers to measure each. I would suggest this method takes out some of the guessing on the centre.

I can see dividing the objective diameter and the barrel by two, but why don't you leave the distance between barrel and scope whole?

#### kcebcj

##### Well-Known Member
For a bolt rifle…….flash hole in the receiver to center scope tube. Use a caliper. Simple to do.

#### morpheus32

##### Member
I can see dividing the objective diameter and the barrel by two, but why don't you leave the distance between barrel and scope whole?

My bad...that is what I meant....

#### Moman

##### Well-Known Member
I figured that's what you meant. I basically do the same thing. I measure with calibers right at the objective but have been wondering how accurate this is with a MOA base. I think it would be good with a standard base but not sure about the MOA. Got to give it some more thought.

#### JRu

##### Well-Known Member
20 MOA would be one third of a degree. Over the horizontal distance of 15" that makes for a vertical difference of less than .1" . So it doesn't really matter much.

If you measure from the front of the scope, just remember to add .05" and you're GTG, that's how little of a difference it makes

#### lamiglas

##### Well-Known Member
thanks for the replies guys!