Help: Sudden negative change in accuracy.
Merry Christmas to you all. I'm looking for some technical advice here. First, I'll describe the baseline condition then what I observed today.
Hardware: Savage 112 on a glass bedded laminated BVSS stock, 22.250, 24" varmint profile, Weaver 3-15x50 FFP tactical mil/mil scope on a 20MOA base, Sierra 50gr Blitzking on a load of Benchmark powder, at ~4000fps.
After trying multiple bullets, powders, and primers I finally worked up the above load last spring with the results I was looking for. Finally ORH. Sweet! Although, as expected, I could see accuracy degrade as the barrel fouled, after cleaning the accuracy would resume. For example: With a non-fouled barrel, I could dial up my Android shooter app, make the elevation and windage adjustments, and I was consistently/consecutively breaking clay pigeons in a gravel pit from 690 yards.
Now, here's where the change comes into play. I purchased a Shilen 6.5x284 Norma barrel for a switchbarrel project and had the gunsmith anchor the barrel nuts on the 22.250 and 6.5 barrels so both could be changed and maintaining proper headspacing. So, today, with a clean barrel, I went out to re-sight in my 22.250 (for coyotes donchaknow) and... to my dismay, my one-ragged-hole gun is now shooting all over the place (between 1" and 4" groups at 200 shooting prone, i.e., consistently inconsistent). (FYI: The smith said he set the 22 barrel back just a scoche before pinning the barrel nut because he wasn't comfortable with the current headspace.)
So, my mind is racing... why SUCH a difference? Scope, action, barrel: All tight. Load: Same as before. Barrel, same, but set back a bit. I suppose the barrel harmonics, etc. could have just been in the zone and now the system is "out of tune". All I can figure is I'm going to need to head to my local range when I return from the inlaws so I can test again from the bench because today I was behind a shelterbelt of trees to stay out of the 20mph wind.
In the meantime, I'd like to hear your input. Thanks in advance.