...and it appears to be my scope.
I've had my Nikon Monarch for nigh on to 10 years. It's served me well on three other rifles. About a week ago, I went out with some loads I was working on and could do nothing right in terms of accuracy. Conditions were good, but my rounds were landing in all quadrants around the bull. No rhyme or reason at all to their pattern. The rifle threw good groups from my bench rest rig up til then if I did my job and the wind cooperated. I wrote it off to something with the loads. Next time out. Same load test, same result. Third time, same test, same results. I wrote off the powder I was testing as a bad choice for accuracy, despite excellent velocity SDs. Fast forward to last Tuesday and Wednesday. I had both days off and was trying some crimp variation tests. Rifle shot to the right about 3.5 inches, so I adjusted it into the bull and got one and a half sets of good 5-shot groups, then back to all four quads. I wrote that test off also to inconsistent crimps, despite having done then with the utmost care. Never suspected the scope. Today, dead still conditions and a different load test using Magtech 230gr FMJs. First three shots went left about 3 inches and I assumed it was from adjusting the scope earlier in the week. Adjusted to bring it back to the bull and again about one to two good groups, then all four quads for the next 25 rounds. Gave up and went home disappointed with the Magtechs other than the one to two decent groups when I first adjusted the scope. I'm sitting here entering the ballistic results and they look good but for the accuracy. I'm not quick to jump to conclusions, but it should have dawned on me after say the first 100 rounds that flew all over the place that I didn't suddenly become a bad shot or that all my loads went down the toilet, but it didn't until I went back through all my targets and range notes for the past week. It's too late in the day to take my reference "known good loads" I have salted away and see how they fly. I suspect something has gone wrong in the scope. The mount is solid, especially since I put some rosin on the ring inserts a month or so ago. The fact that each time I adjusted it significantly, it shot well for a short while before reverting leads me to believe something has gone awry in the reticle suspension system. I have plenty of other good scopes and will take one along with my "known good loads" to give it one last try before I send the scope in to Nikon for a checkup.
It's funny how we put our faith in something once it earns our trust. Sometimes longer than we should. Don't wait until you've wasted over a hundred rounds of reloading time and some excellent shooting days to start questioning. The border between patience and obstinacy is not well marked.
Edit: If you're wondering that's 630 total 450b rounds on the scope. Put about 500 7.62x51 rounds on it the first 9 1/2 years. (G3, FAL, M-14S)
Hoot