I've been mounting scopes for almost 50 years so I know how to properly do it and what to look for if there's a problem. Or so I thought.....
My brother's Model 70 Winchester lightweight won't hold zero. I think it almost has to be a scope issue but here's what we checked.
1. Action screws are properly tightened.
2. Scope bases are tight.
3. Rings to bases and scope to rings are tight.
Rifle has always shot reasonable groups (about 1" to 1-1/2" at 100 yards) with factory ammo and nice groups with handloads. This used to be my rifle so I know it well.
The scope is an original Nikon (now called Monarch) that I bought 20 years ago and payed as much as the highest comparible Leupold scope. The Nikon was clearer and when adjusting it 1 click moved it in the proper direction 1/4" at 100 yards. Always. Now I move it and it impacts far more then what I moved it and when moving it back will go to a different point of impact.
So I think the old scope has finally bit the dust but maybe someone in here can give me something else to think about. The crosshairs look normal. Brother has already ordered a new Nikon scope and rings for it.