I agree with Canazes9, the scope was mounted incorrectly. The M77 is easy to boresight and the problem should reveal itself very quickly.
Because the front and back rings on a 77 are different heights, there is no danger of mixing them up, but what is important to do is make sure the righs are attached to the rifle the same way.
Here is the procedure I use to mount a scope on the 77:
Rings come assembled, do not mix the top half og the rings between the to rings, nor should you change the orientation of the top halves. Clean the top of the receiver and make sure the scalopps are clean also.
Put the rifle in a cradle, without the bolt. Mount the rear ring with the tensioning screws on one side. Mount the front ring with the tensioning screws on the same sight. Make the tensioning screws finger tight with the same tension on both. I like to line up the slots the same way for both rings.
Remove the top halves of the rings, making sure to note the front for each and do not mix them up. You want to put the top halves back on the same ting it came on, with the same holes in the same place. Put these halves to the side.
Make sure the internal travel of the scope is at its middle; crank the knobs all the way to one side and then count the clicks or turns it takes to get to the complete other side. Divide this figure by 2 and then apply the resulting amount to the knobs in reverse. This will give you a scope at its mechanical zero.
Now aim the rifle in its cradle at an object 20-30 feet away, down the hall, out the window, whatever. Aim it looking through the bore of the rifle. Once that is done, WITHOUT DISTURBING THE RIFLE, place the scope in the bottom halves of the rings and then press down on it a little so that it engages in the rings properly.
Now look through the scope and see where the reticle fall. It should be very close to you bore aiming point. Do check that the bore has not moved.
If it looks very close, tighten the tensioning screws, one half turn at a time for each, and keep checking the boresight; Do not tighten the screws on one ring and then the other, do both together a little bit at a time.
When the screws are very tight, reverify the boresight. Now place the top halves on the rings on their respective bottom halves, respecting the initial alignment. Put the screws in and only finger tighten them. At this time, your base is solid, the scope is lined up, but you still need to set the proper distance for the scope to your head and to make sure the reticle is vertical. Once you have done that, by whatever method you think works for you, slowly tighten the screws on top of the rings, in an X pattern: Front ring; front left, rear right, rear left, front right. Rear ring; front left, rear right, rear left, front right. A little bit at a time. What you want to avoid if tightening one side and have the scope get thrown off alignment. Take your time, do it right.
Once finished, check the boresight to make sure you didn't throw it off.
If you cannot get it close enough on the boresight and you think it's going to eat up all your windage, try this; reverse the front ring; mount it so the tensioning screws are on the other side and then check the boresight. If that makes it worse, put the front ring back as it was and then reverse the rear ring.. If either of those make the boresight picture look good, go ahead and complete the mounting as described above.
If you still can't get it to boresight properly, then yes, the Burris Signature rings are something to consider. I use them and I like them very much. You may also consider talking to Ruger about the problem.
