How do you know how much "internal play" your scope has in terms of elevation?

[Paolung]

Trying to figure out if I need a 20 MOA rail or not for my scope, which involves me determining how much internal play the scope has in terms of elevation already.

How do you know how much internal play your scope has in terms of elevation?

If my scope specs say this:

Turret Adjustment (Click Value):	1 click: 0.1MRAD 1 revolution: 10MRAD
Elevation Turret Details:	25 MIL
Windage Turret Details:	25 MIL

does it mean that the scope has 25 mils of total elevation play, meaning 12.5 mil up/12.5 mil down, which translates to about 86 MOA or 43 MOA up/down?

Or am I doing it wrong?

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[The Heretic]

Trying to figure out if I need a 20 MOA rail or not for my scope, which involves me determining how much internal play the scope has in terms of elevation already.

How do you know how much internal play your scope has in terms of elevation?

If my scope specs say this:



does it mean that the scope has 25 mils of total elevation play, meaning 12.5 mil up/12.5 mil down, which translates to about 86 MOA or 43 MOA up/down?

Or am I doing it wrong?

I think you are correct. That was the assumption I made when I was looking at scopes for my .50 BMG.

That said, I believe you can use the totality of adjustment such that you may be able to use all or most of the elevation adjustment if you wish - i.e., you don't necessarily need to start in the center of adjustment. It depends on the rifle and the cartridge. You may also be able to get a base that has adjustments itself - those are out there. It depends on what distances you will be shooting at.

The scope I wound up with has ~23 Mrad of adjustment total, the rifle (AR-50) had a 15 MOA base. So for 2000 yards I felt I had enough adjustment - IIRC - but I was considering getting a base with more elevation, and maybe one with adjustable elevation. I no longer have the rifle but I do have the scope (I am thinking of using it for an AR-10 in .308 or 6.5 CR or maybe for a .338, for which it should have plenty of elevation range).

 

[SageRatSafaris]

Yes, 25 MIL of elevation adjustment means 12.5 MIL up and 12.5 MIL down from mechanical center. If you plan on shooting long range, I recommend using 20 MOA base (or other cant angle, depending on your requirements). In general, down adjustment is wasted, particularly if you have a zero stop. The only reason to not use a canted base is if you only shoot 100 yards. One consideration is that optical performance tends to be best near mechanical center, so if you rarely need to dial up, a flat base is optimum. But if you're regularly needing 20 MOA to hit your longer range targets, the 20 MOA base means you're using optical center for those targets.