agingcowboy said:

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Good stuff, lots of ideas here that I'll give a try. I did take the rings off the bases and checked the bases as well. I didn't remove the rings from the scope, just made sure they were each torqued properly.

It's been a couple of years, but I did add a monopod that attaches to a short rail that connects to the rear sling stud. Hadn't consider this, but could that somehow screw with precision?

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It can. Take the monopod, rail, and sling stud completely off the rifle and re-shoot.

Also, try dry firing the rifle to see how it behaves. My 300 WM is light and has a fairly a slippery stock, so when I dry fire with front bags I noticed that it jumped around like mad. I have to hold the fore end between my left index and thumb, while using my other three fingers to pull it into the front bag. It makes a difference between a 2.5" gun when shot free recoil, and this sub-MOA.

Dry fire it with the monopod on, and with it off. See how much the scope's reticle moves around.

I would do that first as it is at least easy. Also....I noticed you have two piece mounts on your scope. Were the rings lapped before the scope was mounted? If not, or you do not know, I would have that checked before you install another scope. If the rings were not lapped or lapped incorrectly over time of shooting the rifle it could have been putting stress on the scope itself and could be causing your issue...........but I would shoot another group of a different factory round first.
I have had some clients that had similar issues and a couple of times it ended up being the scope as the rings were not lapped and had in a sense kinked the scope over time.

Probably stupid and way off base but when my groups fell apart it turned out I needed glasses.

Sure anything but stupid. More relevant than most think. Very good point.

jpd301 said:

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Probably stupid and way off base but when my groups fell apart it turned out I needed glasses.

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This is REAL