Rifle Scopes Measusring Scope Height?

[Punisher29073]

When measuring scope height to enter into a ballistic calculator, such as Strelok, does it make a difference if you have 20 moa base and where should you measure, front, middle, or rear of scope?

Ryan

 

[Rob01]

Doesn't matter but I always measure in the center at the windage knob because it's easy to get reference points.

 

[Layton]

Not that it matters but I vote to make Rob's post a sticky. Question comes up often enough.

L

 

[AussieShooter]

+1

 

[peewee]

So, if my ring height says 1.46", is that not the height I use? Do I actually need to measure center of barrel to center of mounted scope? Thanks I'm still learning.

 

[Layton]

So, if my ring height says 1.46", is that not the height I use? Do I actually need to measure center of barrel to center of mounted scope? Thanks I'm still learning.

Correct. Just like it Rob's pics. Close counts as your cross-hairs won't be centered in the scope tube perfectly.

L

 

[Punisher29073]

That is how I have done it always, yet..... On my current 300WM, My Strelok App is way off as far as POI at 200 & 300 yds. This happened to multiple bullets and loads. Way off to me in this case is about 1 MOA. I have chrono'ed the loads out of this gun and entered in the BC for the bullets. The only variable I could come up with was maybe I measured the scope height wrong. Is ballistic software this unreliable usually? I have been happy with my 223, 243, and 308. What am I missing?

Ryan

 

[Rob01]

Must be something else. Being off a full MOA would take your scope height measurement to be off by almost an inch. Go back over every input and make sure you didn't put something in wrong.

Did you run a tracking test on the scope?

 

[Punisher29073]

I haven't run a tracking test, but I didn't have any trouble when zeroing. That will be my next step. Thanks for your help.

Ryan

 

[scudzuki]

The difference between measuring the scope centerline to bore centerline at the mount vs. the objective bell is less than 1/16" with a 20 MOA base.
Picking a spot where you can see the entire diameter of the barrel (easier to estimate the centerline when you can see the entire tube) will influence the accuracy of your measurement more than where along the scopes length you measure it.

An incorrect value in this part of the equation becomes less critical the farther out you shoot the farther out you are shooting.

I used 2.25" for several of my rifles when I initially set them up in Strelok (Android App) and it's never been more then a tenth of a mil off, so I never bothered to actually measure it.

Joe