I've mounted scopes on literally dozens and dozens of different rifles and have never needed a shim for any of them, never. Some simple things that might have caused this problem could be something as simple as mis-matched rings and bases. If someone used rings to mount a scope that might have had differing heritage, it could be very easy to imagine very slight differences in actual height those rings gave.

It's a well known fact that one brand of medium ring is not always the same height as another brand of "mediums". Perhaps that might be the cause.

Even though it's a Leupold and they are well known to build high quality scopes, the scope might also be defective. For the record, I've never owned a Leupold that failed in any manner, but never say never.....

How new is the rifle? Unfortunately, I've read several comments lately about Remington made products that have not been "up to snuff", quality wise. It will only take you about 2 minutes on a popular lever gun owner's forums to read lots of bad things about that company's new owner. (happens to be Remington)

As I've already mentioned, I've simply never run into a rifle that needed that type of mod, but I also normally purchase new, quality rings and bases for any rifle, new to me.

Good luck!! 

Great point about the potential mismatch in bases or rings - I had not thought about that.

I have had several 700's and they were great rifles.

I too have had wonderful success with Leupold products - they are great and their customer support is superior too.

I will wait and see what happens with this contest for the 300 and then decide on whether or not to pursue the 30-06 - I need (OK, want) and elk rifle!

If he couldn't get it to adjust up enough to get the bullet on zero, why would he put a shim UNDER the REAR mount?  That makes no sense unless his problem was just the reverse of what you are saying he told you.  If you get a good deal on the outfit, I would just take the scope off and start all over even if I had to replace the mounts.  I think the dual dovetail system Leupold has available is better than that rear adjustable one that is on the gun now anyway.  You may just be able to replace that rear one and take care of the problem if, in fact, the guy knows how to sight in a scope in the first place!