Sight height?

[elkslayerjc]

How do you figure out what the sight height is of your scope to the center of the bore is? Is there a specific way to measure this without knowing the height of the rings?

 

[nwolf]

1) Remove the stock.
2) Use a set of callipers to measure theoutside diamiter of scope tube.
3) Divide that by 2.
4) measure the diamiter of the barrel at a point under the scope tube.
5) devide by 2. Add that answer to the first one and set aside.
6) measure from the top of the scope to the bottom of barrel at the point you checked the barrel.
7) subtract the first number from the second. ta da.

 

[RDM416]

The process from nwolf is the best and most accurate way to measure sight height. you can also use a set of calipers or sometimes I will use a 6" steel scale and "eyeball" the center of scope tube to the center of the barrel. I can usually get to within 0.1" or less that way, and I don't have to remove the stock. However, the method from nwolf is the most accurate.

Also, as I assume you know since you asked the question, it is very important to get this right if you are using a ballistic program. If you are off a couple of "tenths" or so it will have quite an effect on the ability of your program to give you accurate down range dial up info.

 

[kcebcj]

Another way is to just slide your bolt back until it's even with the rear of the scope and measure center to center. This only works it the bolt fits snuggly in the receiver. If the scope is set way back or the bolt is sloppy this won't work. To do this on my rifle the bolt only has to move rearward two inches.

It will get you close enough but if you need more accuracy remove the stock and use calipers as nwolf noted.

 

[KRP]

You don't need this measurement accurate to four decimal places...or three...or two...which is good because you probably can't do that. .1" difference in sight height will cause an error much less than most people are capable of shooting. Pull the bolt back, measure firing pin to scope tube then add half the diameter of the tube. Or pull the bolt back and eyeball to the center of tube/rings.

 

[RDM416]

You don't need this measurement accurate to four decimal places...or three...or two...which is good because you probably can't do that. .1" difference in sight height will cause an error much less than most people are capable of shooting. Pull the bolt back, measure firing pin to scope tube then add half the diameter of the tube. Or pull the bolt back and eyeball to the center of tube/rings.

I agree with KRP that .1 is "good enough" for this measurement, but also advise to not be sloppy about it. At closer ranges errors in this measurement can have a pretty minimal effect. However, as you reach on out there to 1000 yards or so the error can become enough to really matter. After all, with long range shooting it often comes down to a combination of small errors that add up to enough to cause a miss rather than 1 big thing.

Input all your data into a ballistic program, set it for 1000 yards then vary your sight height in increments of .1 and you will see the difference it will make. It may only be 1/2 moa at 1000, but that is 5".

 

[MontanaRifleman]

The way I do it without taking the stock off is to...

- measure the OD of the barrel just under the front end of the scope

- measure the OD of the front end of the scope

- add the two measurements and divide by 2

- measure the distance from the bottom of the scope to the top of the barrel and add to the the previous figure. That's your scope height.

If your measurement is accurate to the closest .1", you're GTG.

-Mark