Measuring scope height

[2cams]

For ballistic calculators scope height over centerbore is required.
I can go caliper method, but it seems imprecise.
Do you guys use calculations measure scope height? Any better than others?
I probably wouldn't be able to tell the real world difference if I input 1.6 instead of a hypothetical "true" 1.7 or 1.8, but curious in general about the consensus (if it is possible in the optics thread, or 24HCF in general!!)

 

[Hair Trigger]

I don't think 1/10" will matter much, if at all. I measured from the breech, with a small tape measure from bore center to surface where the scope rings mount, and then added the advertised height of the rings I used, and then half the barrel diameter of the scope tube. Close enough to shoot 1100 yards and hit what I pointed at. (.308 and 6.5 Grendel)

 

[Krogen]

I measure the barrel diameter at the scope ring, divide it in half and add the height between the top of the barrel and top of the scope tube, then subtract half the scope tube diameter. Depending on how big the scope is and how it's mounted, this can usually be done with calipers. Failing that, a small straightedge or tape measure will get you close enough.

 

[WR Moore]

While the computer generated ballistics tables are convenient, you still have to shoot your rig/load at the given ranges-or at least pick several to give your an error bracket-to see what it's actually doing. The differences there can be greater than a slight difference is scope height.

Then there can be differences resulting from temperature, barometric pressure, altitude, if your ammo was in bright sunlight for an extended time, different lot of brass/powder.......If you're looking waaay out there, there are ballistic calculators that'll read atmospheric conditions and spit out a density altitude that'll take all the variables-except cross winds and ammo variations-into consideration. Most of us just record sight corrections during different shooting conditions in a data book and refer to that.

 

[Rodan]

I usually just use a straightedge. On many rifles the top of the forend is even with the bore center, so there to scope center and you have your measurement.

Ballistic calculators are an approximation, and get you in the ballpark, but you still have to work up the dope for your individual rifle/load to be precise.

 

[marinevet]

Center of bore to center of scope. The people at Kestrel, which is the manufacture of the ballistics calculator that I use says with in 1/4" is close enough.

 

[H Richard]

I just put a cleaning rod through the bore, and letting it stick into the open chamber took a ruler from it to the center of scope. Using this measurement (along with a lot of other info) had Leupold make me a custom elevation knob and once sighted at 100 yards, will dial in all other distances. I did a cold 1 shot kill on a Prairie Dog at 507 yards just dialing it in on the turret (and allowing for 7 mph right wind).