20 MOA scope mounts

[alamo308]

To ensure the scope will have the needed elevation adjustment available to go out to 1000 yards, I got a set of Nightforce 20 MOA scope mount bases for my Winchester Model 70 receiver, and am ready to install them. But now I am stumped; since my only available practice range maxes out at 300 yards, how should I practice? Should I:

• Not install the bases, but zero the scope with the current non-20-MOA bases, and then switch mounts for a 1000 yard event?
• Go ahead and install the 20 MOA bases, and practice on a 300 yard "thermometer" target that shows calculated impact points for 800, 900, 1000 yards above the POA?
• Try another approach?

Suggestions welcome...

 

[Mikewood]

Shoot the gun with your 20 MOA base dialed down 100%. You might get lucky and be dead on. Also Depending on your reticule you can use the top duplex bar or one of the dots on a milling reticule as a close Aiming point. At worst just aim for the bottom of the target frame. Even put a small aimin dot there. Whatever you do get both your dead center zero range and max up and max down and work mathematically from those zeros to get your minutes of movement per yd. Also shoot a box and a line thru the turrets movement to be sure the turrets are tracking square.

 

[alamo308]

Shoot the gun with your 20 MOA base dialed down 100%. You might get lucky and be dead on. Also Depending on your reticule you can use the top duplex bar or one of the dots on a milling reticule as a close Aiming point. At worst just aim for the bottom of the target frame. Even put a small aimin dot there. Whatever you do get both your dead center zero range and max up and max down and work mathematically from those zeros to get your minutes of movement per yd. Also shoot a box and a line thru the turrets movement to be sure the turrets are tracking square.

Thanks, Mikewood. Excellent suggestions! Kind of what I had in mind, but just couldn't put all the variables together and come up with a coherent strategy. The scope is a Leupold Mark AR 6-18x40 with the BDC mildot reticles, and I'll be shooting .308, so I should be able to use the combination of data to help calculate the adjustments. ...Now - got to just find time to get out to the range!

 

[Mikewood]

Using your scope choice say you zero your rifle and it falls on the scopes mechanical zero which never happens. From center you can adjust 28 min up down right of left for a total movement of 56 minutes. So say the turrets are exactly center up down right and left. now add your base 20MOA of elevation. Using your leupy mil reticule it has 5 mils from center to the top bar. A mil is about 3.5 MOA. So you got 17.5moa. using the top bar as point of aim you should be close enough. Or just dial down the 20 minutes and shoot at the center of the cross hairs. You still have about 8moa to play with if the scopes mechanical zero does not match the rifles. That's the 100 yd zero.
Say your drop is three minutes at 200 yds. Just drop to the first mil and shoot.
300 yds and 5 minutes drop? Drop to the second mil dot. It's easy!
You just need range and windage to get hits. That and a good "bible".
Learn to think in minutes.
2" is 1 min at 200yds, 4" is 1 min at 400yds.

 

[rnuovrcj5]

Your scope should have enough adjustment to be zeroed at 100yds even with the 20moa base. You then make the normal elevation adjustment for range. The 20moa base just allows you to have more upwards elevation than the flat bases by moving the crosshairs towards the bottom of the adjustment range in the scope. This is what alows you to adjust for longer ranges. You lose downwards adjustment but when do you ever really adjust for under 100yds?