I bought a Stainless Model 70 338 four years ago that was a complete POS, it shot patterns instead of grups. I'm talking 3" five shots as about the best it ever did. Winchesters quality control missed out on it big time, for instance the bolt face was never machined.
A new stock, #4 Kreiger, and a bunch of good gunsmithing and now it shoots with the most accurate stuff I own. The first five after I got it back was 5/8s at 100 yards
I have another in a Ruger 77 that's 20 plus years old that shoots almost as well, but only with maximum loads and 250 gr Noslers. I haven't found anything else it likes.