I would have to agree, these are nice actions. I had a Stainless Classic in 300 WM. What a beauty! I say had one because I could never get it to shoot. The tolerances in the chamber were horrible, lots of shoulder stretch on new brass and a bunch of bullet jump. New brass could be fireformed but I never could get bullets to seat close enough to the lands for any decent accuracy. Partly due to limited length of magazine but mostly due to a reamed chamber.
I would try what Landcbeitner recommended and if that didn't work, I think I would rebarrel it. I am not well experienced on custom rifles
but I do remember seeing a lot of custom builders using the model 70 action on their builds. I wish I still had mine to do something like this with.