Yes, when an E or W adjustment is near a mechanical limit, the inside tube of the scope is close to the outer tube the mount rings clamp onto. Adjustment range is typically limited.
Those PST 6-24 models have about 65 MOA elevation adjustment range. I don't know how much adjustment range there is from the scopes axis to the 100-yd. zero settings its at. All the scopes I've checked have a much greater adjustment range up and right from their axis than left and down. I therefore think your rings axis is a long way off from the rifle barrels bore axis. That happens when the barrel thread axis in the receiver are not in line with the receiver axis the scope mount bases are aligned to.
The first thing to do is count then write down the clicks to mechanical limits down for elevation and left for windage, then title them "100 yd zero's from down-left stops."
If you know how to zero the scope adjustments by twisting it in V cuts in a cardboard box, that's the second thing you should do. If not, let me know. Once the adjustments are at the optical and mechanical center ad determined by the V cut and twist process, count and record on paper the clicks down and left from that point then title them scope adjustment zero's from down-left stops.
Third, compare both sets of zero's. If everything is perfect and the scope ring axis is parallel to the bore axis, if you check the bore sight of the bore to line of sight of the scope, they're both pointing/aligned to the same place. If not, either the rifle's receiver or the scope bases or rings axis isn't aligned with the bore axis.
There are scope mounts that can be adjusted to put the scope axis parallel to or below the bore axis. Even if a 20 MOA base is put on the receiver, any misalignment between receiver and barrel will be transferred to the angled rail. Talking with the man who made the first angled rails back in the 1960's enlightened me to all sorts of issues one has to deal with when all the parts involved are not aligned with each other.
These rings and bases are excellent to mount the scope with a down angle like rails do. But don't interfere with charging internal box magazines like most rails do. With a .020" offset insert in both rings 6 inches apart, that'll give about 25 MOA offset of the scope axis to the scope base/receiver axis.
http://www.burrisoptics.com/signature-rings
From Burris' web site:
Pos-Align® Inserts
Pos-Align Inserts guarantee perfect centering and maximum scope-to-ring contact, so you get all the clarity, sharpness, and brightness your optic can deliver.
- Virtually sight in your gun without moving the scope adjustments
- Corrects any misalignment caused by receiver holes drilled off-center
- Corrects for bases or rings being slightly off center
- Makes expensive tapered bases or shimming for thousand-yard shooting a thing of the past
