ArizonaShooting.ORG

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 scope 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 believe the correct way and the way I do it is this. First measure your scope bell dia. and divide by two. Write that number down. Then measure the barrel dia. just in front of the scope bell and divide that number by two. Write that number down. Then measure the gap between scope bell and barrel and add that to the other two numbers and that will give you an accurate scope height within a thousandth or two. Most apps give the standard 1.5" when in reality most are closer to 1.8" - 2" especially with todays large dia scope tubes, picatinny rails and 50-56mm scope objectives. The difference between 1.5" and 1.8" will be the difference between an accurate drop table and one that will never match up to anything you ever fire in the field. I hear people at the range all the time complaining about their expensive shooting app not giving correct solutions. #1 thing that they haven't input correctly is sight height.

Get it close and you won’t notice the difference. It’s a variable you can tweak to dial in your calculator if you find you’re a little high or low across distances. What lines up best with your calculator output may not be what your scope height actually is.

To see what difference it makes, just run the calcs at 1.5” vs 2.0” vs 2.5” and compare the tables. I just ran it for one of my loads and a half inch equated to less than 2” at 500 and less than 4” at 1k. Other variables are going to bite you long before scope height does.

Crap in equals crap out. The more accurate info you can give your calculator the better off it will be. I always measure the sight height the way I described above. I use a magneto chronograph to get an accurate velocity and I use Litz measured ballistic coefficients not advertised. I also input my zero conditions, temp, elev etc. Doing this my Applied ballistics app will generate a shooting solution that is either dead on or off not more than a click at any given range. When using a shooting app the only variable that should really be changed is the click adjustment which can be checked with a tall target test. The rest should all be known hard info. Adjusting BC or velocity may bring things closer at certain ranges and may work fine for banging steel, but if you want first round hits on game or smaller targets all of the inputs should be as close to exact as you can make them.

There are different calculators and different calculation methodologies because none of them are perfect. There isn’t a single one out there that doesn’t require tuning.

Now that’s some science. Take notes Fauci