Again, I really appreciate all the info and advice...you all are a good crowd to converse with.
So I did as was directed...I loaded up some rounds with the original load that worked so well originally, 175 grn SMK, 10 grn TB, WLR, and Win brass. I fired 5 rounds without the suppressor...nice group of about an inch with one flyer a couple of inches away, but that was a problem with the trigger mechanism, that is, my trigger finger;-) No issues with tumbling...nice clean holes at 100 yards. All rounds were carerfully single fed.
Next 5 rounds through the suppressor...again, nice group of 4 rounds at about an inch or slightly more with one flyer a few inches away, but not 7-8 inches as before. Now I am beginning to think it was all operator error.
So I loaded up 10 more just as before, but before going out to shoot I put my stock between my legs and gave a little pressure to the suppressor to ensure it was good and tight. On the first group I had only snugly hand tightened without wedging the stock between my legs.
So I go out and shoot...first two rounds about an inch and a half apart and grouping as before. Next three rounds fly 7-8 inches high and right, and I begin to think to myself, "self, you tightened that can down differently this time." I loosened the suppressor, then snugly re-tightened using only my right hand on the suppressor as with the first 5 rounds. The next 5 rounds grouped at about 1.5 inches...if I throw out the flyer, the four were within 1 MOA.
Now to explain...I gave my rifle to my gunsmith/machinist to do a little work on the threads so that the suppressor didn't work itself loose with standard velocity rounds, and he did some machinist's trick so that when I tighten the suppressor down, there is extra space now and that causes the suppressor to stay in place without working loose. Before he did this work, I had been accustomed to really cranking down on the suppressor with the stock between my legs.
Apparently, since the new thread work, I have been cranking down way too hard on the suppressor and likely putting it off center. With the suppressor snugly tightened with only one hand on it and one on the stock, the issue is resolved.
Good gracious, who would of thunk it?
Jasper