I have had a few rifles like yours over the years, they are nothing but frustration. Like you I have tried every trick in the book on them and they just respond with teaser groups but no consistency. I have tried different stocks, different bedding, different scopes and mounts, it seems as though an occasional rifle just will not respond.
Back in the early 90's when the 700 first became available in 260 Rem I bought one and it was the absolute worse grouping,most inconsistent rifle I have ever owned. I did all of the usual tricks without making much headway - I finally took it to them smith to have the action trued, barrel crown touched up, etc. When I picked it up he said that he had never seen a 700 as out of tolerance as that one was. When he trued the bolt there was a high spot on it about 1/3 of the way around the bolt just behind the locking lugs, both lugs had to be trued to make good contact and the bolt face had to be trued. It shot ok after all of that but even then it was no better than any of my other 700's.
Sometimes you have to accept that you may have a POS and move on to a different rifle.
drover
