What is Your Method for Measuring Scope Height?

[Longshot231]

I have a few techniques for measuring scope height for use in a range finder/ballistic calculator.

However, I'm curious. What does everyone else do to measure the height of their scope above the bore?

For a follow-up question how far off the actual height do you think you can be until it shows a significant difference in the firing solution given by your range finder or ballistic calculator?

 

[OLD308]

I took digital calipers and alined them with the center of the closed bolt and the center of scope tube. If you have a Kestrel you can play around with the different measurements. Less than 1/4" variance doesn't seem to bother it.

 

[Combloc]

Strelok's site says this:

Measure the diameter of the scope bell (on the end, from side to side, not the circumference!) and divide that number by 2. Measure the barrel diameter just under or ahead of the scope's bell, also divide by 2. Last, measure the gap between the bottom of the scope bell and your barrel. Add all 3 resulting numbers together to get your sight height.

 

[RackOpsTactical]

I use calipers from the center of the brl to the split in the scope rings.

 

[sabrecross]

 

[Longshot231]

I've used that method except that sometimes there is too much play in the bolt when it is pulled from the receiver. I've got a few rifles with a lot of bolt wobble and others where it is really tight with very little play.

If there is a lot of play with the bolt, I resort to another method of measuring the height.

I've thought about another technique to get a more exact measurement but haven't tried it.

You would need a piece of plain white paper with a dot or X in the center. In addition, you would need to use some sort of laser device that is typically used to obtain a rough bore sight of a rifle prior to going to the range. It can be either the cartridge shaped laser or the muzzle mounted device.

For this method, I would start by adjusting the windage and elevation knobs so that they are centered.

Then I would secure the rifle in something that will hold it and with absolutely no movement. The rifle would be pointed at a wall that is only a few feet away.

On the wall, I would place the piece of plain white paper with a small dot or X on it. Adjust what ever device is holding the rifle so that the dot or X on the paper is in the cross-hairs of the scope.

The parallax adjustment would have to be dialed down to the shortest range and the scope set on a low power setting to get the cross -hairs on the dot or X.

The next step would be to insert the laser and turn it on.

Ensure that the cross-hairs are centered on the dot or X while the laser is emitting a red dot on the paper.

The final step would be to measure the distance between the dot or X on the paper and the laser's red dot. That should give you the exact height of the scope above the bore of the rifle.

The divergence caused by the 20, 25 or 30 MOA bases should be so minuscule that it should not cause any big problems with error.

So what does everyone think? Could there be any problems with my theory on the laser technique of measurement?

I haven't tried it myself but will as soon as I can find a place on my crowded wall to hang a piece of paper.

 

[AMGtuned]

I was just about to post a similar question. I use Strelok Pro. I have always entered 1.47 for the height, because I've used it only for rifles with American Defense Recon scope mounts. Their height from top of rail, to centerline, in my case with 30mm, is 1.47. However; height from bore centerline, to top of rail on AR10/AR15 is about 1.2", if I'm not mistaken. Please correct me if I am wrong. So, I have been thinking; and where it asks for "scope height", I'm assuming that is height over bore (since we are using the app for bullet trajectory, and bullet leaves bore center), and I should add the 1.2" to the mount height of 1.47". Final height being 2.67". Am I correct in this thinking? 1" of scope height difference is definitely enough to screw up a ballistic solution, I would think.

 

[dbshiner]

+1 on the calipers measured center to center

 

[Longshot231]

I was just about to post a similar question. I use Strelok Pro. I have always entered 1.47 for the height, because I've used it only for rifles with American Defense Recon scope mounts. Their height from top of rail, to centerline, in my case with 30mm, is 1.47. However; height from bore centerline, to top of rail on AR10/AR15 is about 1.2", if I'm not mistaken. Please correct me if I am wrong. So, I have been thinking; and where it asks for "scope height", I'm assuming that is height over bore (since we are using the app for bullet trajectory, and bullet leaves bore center), and I should add the 1.2" to the mount height of 1.47". Final height being 2.67". Am I correct in this thinking? 1" of scope height difference is definitely enough to screw up a ballistic solution, I would think.

You always want to enter the height over the centerline of the bore. Keep that in mind if you are shooting different caliber rifles.

 

[Deleted member 10043]

Ruler

 

[Sig Marine]

Ruler

Yep...no need to overthink this...use a ruler to measure from the gas port on the receiver to the center of your scope tube.

 

[ken4570tc in WY]

With a 20MOA base the scope is not mounted parallel to the bore, so do we measure at the objective, the ocular or the turrets and why?
I haven't seen it discussed in this thread yet.

 

[Sig Marine]

Turrets. You want to measure as close as possible to the reticle. As noted in a post above, a “dead-nuts” measurement is not necessary so measuring at the turrets will be close enough to the vinincity of the reticle to give you a good working number.

 

[Longshot231]

With a 20MOA base the scope is not mounted parallel to the bore, so do we measure at the objective, the ocular or the turrets and why?
I haven't seen it discussed in this thread yet.

 

[ken4570tc in WY]

Turrets. You want to measure as close as possible to the reticle. As noted in a post above, a “dead-nuts” measurement is not necessary so measuring at the turrets will be close enough to the vinincity of the reticle to give you a good working number.

That's what I thought and have always done but the replies to this thread and others drove me to ask for clarification. Thanks!

 

[ken4570tc in WY]

I've got an old operating system that doesn't get updates to let me view newer video formats. Sig Marine gave me an answer that confirms what I had been taught, "Turrets."

 

[wade2big]

I use a tape and get close. Scope height makes very littl difference asblong as you are close.

 

[bax]

I have a few techniques for measuring scope height for use in a range finder/ballistic calculator.

However, I'm curious. What does everyone else do to measure the height of their scope above the bore?

For a follow-up question how far off the actual height do you think you can be until it shows a significant difference in the firing solution given by your range finder or ballistic calculator?

I use Badger rings and bases. Download the drawings from the badger site. Using the ring drawing determine distance from ring center to base then add that to the distance from the base top to receiver. Look up the receiver diameter and divide by two.

Or, use a ruler. Measure from the middle of the scope eyepiece to the middle of the firing pin.

 

[Forrest84]

Just use calipers from center of turret to center of barrel... boom done keep it simple

 

[fastfwd]

how far off the actual height do you think you can be until it shows a significant difference in the firing solution given by your range finder or ballistic calculator?

This is something you can discover on your own by just entering different heights and comparing the results.

For example, jbmballistics.com gives these elevation numbers for 1.5" and 2.0" scope height (Hornady 143gr ELD-X, 2650fps):

    Range   1.5"    2.0"
    (yd)    (mil)   (mil)
     100    -0.0    -0.0
     200    -0.6    -0.5
     300    -1.3    -1.2
     400    -2.2    -2.1
     500    -3.2    -3.0
     600    -4.2    -4.1
     700    -5.4    -5.3
     800    -6.7    -6.5
     900    -8.1    -7.9
    1000    -9.6    -9.5

So even if you just eyeballed the scope-height measurement without calipers or a scale, the error from your ballistics calculator would generally be less than 0.1 mil.