I think what you are describing are "phantom clicks," which means that the turret is turning, but the erector is not moving.
Your erector might look like the bottom image in the stack. It is possible that it is hitting the inside of the scope tube and stopping. (This doesn't mean the scope is broken). The erector spring holds tension against the erector tube, and the windage turret presses the erector tube against that spring.
I'll bet that the 2 1/2 turns of phantom clicks are when you're dialing the turret out.
Right? Which would be counter-clockwise on most scopes, though I'm not sure on the Nikon.
Do you have offsets installed in the Burris Pos-Align rings? Check the numbers on the polymer inserts and make sure they are all zeros. Otherwise, you'll have extra elevation on the scope (extra elevation from the Pos-Aligns is fine when you need it, of course).
Having had another scope on the rifle before which worked fine doesn't necessarily mean that the mount is straight with the bore. Some scopes have more adjustment room to accomodate a crooked mount.
I would remove the scope, and then center the windage and elevation turrets. The proper way to do this can be found HERE...
...but you could also just dial the turrets end to end, and count the clicks half way back to center. That should get you within 3 MOA of center (or thereabouts).
If you just dial the scope turrets and count the clicks back to center, you won't have to remove it from the rifle. Once you've got both the windage and the elevation
turrets dialed to approximate center (or exact center if you follow the instructions in the link above) then you'll want to bore sight the scope and see how far off the elevation and windage is.
If you have to dial the windage turret more than one turn (or 10 to 12 MOA) from center to get your zero--there is something wrong with the mount.
It could be that one of the Pos-Align rings has an offset in it (check the numbers on them) or it could be that the Weaver bases aren't lined up right with the bore.
I just don't want to see you send the scope in, wait on them to check it out, and then find out when you get it back that the problem is still there...
Good luck. [img]/ubbthreads/images/graemlins/smile.gif[/img]
Edit: I didn't notice the last line of your post. You indeed to have the offsets in your mount. And you obviously know what they are for. I assume you've got +20 MOA under the rear of the scope--right? So basically, you do have the erector moved low for the 100 yard zero. This totally explains the lack of windage (left to right) travel. The erector will be "bottomed out" in the tube. One way that you can fix this--since you already have the offset inserts, is to swivel the inserts to either 4 o'clock or 8 o'clock, which will move the scope tube to one side or the other.
I am totally convinced there is nothing wrong with your scope. [img]/ubbthreads/images/graemlins/smile.gif[/img]