Rifle Scopes Question regarding scope height

[Flynn]

I recently mated my new TRG 22 with a S&B 3-12x50 PMII. Here's a pic of the rifle and a target from my first and latest range trip:

9 shot group:

My point isn't to chest thump or boost my ego by posting the pics. Rather, it's to give you a better idea of the rig I'm speaking of.

I do not have a canted rail on this rifle (it's the factory Sako rail. using Talley medium rings). My intended purpose for this rifle is range/bench shooting and hunting. I never intended this rifle to be a 1k yard rig, 900 at most (hence the 20" barrel choice).

To the point! I do not know how to properly measure the scope height to input proper data into a ballistics calculator. I've always been taught that the closer to the barrel the scope sits, the better and I always leave that input data at the default 1.5".

Even without the canted base and medium rings with a 200 yard zero, I still have 13.5 mils of upward adjustment left on the scope (according to the ballistics data, I'm more than good enough to reach out to 900 yards).

Here comes the stupid question! How does the scope height affect bullet drop/ballistics info (long range) and which is more beneficial to long rang shooting, less or more than 1.5" scope height? Why is 1.5" always the default scope height?

 

[BapZander]

Re: Question regarding scope height

The reason for scope height in a ballistic calculator is the bullet comes out of the barrel but you're looking through the scope.

Say your scope is exactly centered and parallel to the bore. The ballistic calculation says that the bullet will drop 1" at 100yds. If you adjust your scope 1moa, the bullet will hit 1.5" below POA - because it started 1.5" below POA.

1.5" is just a reasonable default number. Just put in a number that is an accurate measurement between center of bore and center of scope for the output of a ballistic calculator to be as accurate as possible. Neither high or low is 'better'.

 

[TiroFijo]

Re: Question regarding scope height

Flynn, great rig and excellent shooting!

As Bap said, the 1.5" sight height value is just a convenient default value, mostly for hunting rifles. Tactical scopes and mounts are usually higher. No advantage either way, but you have to imput the correct number in the program.

Just measure the distance between the center of the scope and the center of the bore. If your accuracy is within 1/8" or better (and you can get this with a simple ruler), you are good to go.

 

[Rob01]

Re: Question regarding scope height

Picture might only be worth 500 words in this economy but it might help. Center of windage knob to area that is about center of bore line. As long as you are withing a couple tenths of an inch you will be fine for shooting longer distances. If you plan to shoot inside 100 yards as in down to 25 yards and in then get within .1" as the sight height is more crucial there.