Re: Which AI mount for S&B 3-12 DT
That depends how far the shooter intends to shoot.
If a scope is perfectly built, with equal amounts of up and down reticle travel, one can assume that half the reticle travel is available as "up" elevation.
But one must subtract off that "up" elevation the amount of travel it takes to achieve the desired zero.
If one decides on a 100-yard zero, compensation for the scope height above bore and the drop to 100 yards will require somewhere in the vicinity of 4 MOA.
So, if the scope you mentioned actually has 55 MOA of travel, that means only about 27 of it is available as up elevation on a flat base. Subtract off the 4 which is necessary to achieve a 100 yard zero, and that doesn't leave enough to get a .308 to 1000 yards.
And that's why the necessity of an inclined base.
Some S&B scopes, like the 5-25X56, have enough reticle travel not to require an inclined base. Many of them do require an inclined base for practical use.