Hi Ratltrap,
Could you tell me more about Lug setback.
I have a Whitworth 375 H&H. Just bought it in Nov from a friend. It was customized when he bought it 8 years ago.He shot 20 rounds to zero the scope and then he stored it in his basement gun cabinet with no humidity controls for eight years.
I shot it in Nov. 2006 and it grouped an inch or less over the course of forty rounds. I cleaned it over Christmas and took it out two weeks ago and had a shift of impact 9 inches right and 6 inches low, at 25 Yards!!!
The strange things about this are 1) I didn't take the gun apart, only used a Bore guide with a nylon brush and Barnes Bore cleaner, 2) The gun still groups as tight as it did back in November.
The real problem is that my friend doesn't recall the Customizer, nor does he have the paper work, so I don't know if the barrel was originally free floated. I didn't check this when I bought the gun. All I know is, that now it is not free floated. There is contact about 1 inch from the front of the stock, and seems to have contact on the right side to about 2/3's of the way around the barrel.
I would have thought that if humidity change would have caused the stock to shrink in my safe with desicant, that any new barrel pressure would not only cause a shift in impact but would stand a good chance at increasung group size as well. I didn't want to take the gun apart until I have a chance to shoot it some more and see if I get any more changes.
It is the continuing good groups that causes me to question something internal to the scope? Again I would think that any looseness in mounts or screws would degrade the group size as well as impact. Any one ever have a scope have such a shift?
Thanks for any thoughts, insights, or experiences. Specifically the lug set back and what that would do from an impact vs. grouping stand point.