Suggest that before you shim that you centralise elevation adjustment ( wind all the way down and half way back).
Then set up a tall 50 yard target with an aiming mark at the top, and fire 1 or 3 rounds to measure total drop at 50 yards(1,800 inches).
Divide drop in inches by 1,800 and multiply by distance in inches between centres of your scope rings will give you a ball park figure for thickness of shim to insert between bottom of scope tube and the top of the lower rear scope ring.
Suggest that before you shim that you centralise elevation adjustment ( wind all the way down and half way back).
Then set up a tall 50 yard target with an aiming mark at the top, and fire 1 or 3 rounds to measure total drop at 50 yards(1,800 inches).
Divide drop in inches by 1,800 and multiply by distance in inches between centres of your scope rings will give you a ball park figure for thickness of shim to insert between bottom of scope tube and the top of the lower rear scope ring.
I also suggest this very much. I’m certain you’re aware, but use care when you are bottoming out the erector (either up or down) during this adjustment. While “modern technique” in long range shooting is to “dial the turrets”, the older optics really weren’t designed to be cranked on repeatedly. Just treat it with the respect it deserves! I also suspect a base issue. It’s normal in long range shooting to instal what is referred to as a “20MOA base” (they come in 0, 10, 20, 30) to allow say a 200-300y zero in the bottom of the scopes adjustment range. This allows the ability to “dial” the turrets for using the reticle directly for aiming at distances past 1000+ yards dialing the elevation directly.
Anyhow my .02. You may also want to measure the rough height on each base using a micrometer or fine ruler. Another way to confirm the problem without firing a shot.
