Neat gun.

Are you sure it's a .280?

What I mean is I wonder if somebody checked the chamber and found it was just about like a .280, was unaware of the 7x64 and described it as a .280.

I wonder if it is actually a 7x64?

Some years ago there was a Ruger M77MKII in 7x64 that sat on Gunbroker, and sat, and sat... In fact, IIRC for over a year or maybe even two. The guy wouldn't budge in price but there were many evenings I almost "pulled the trigger" on that one. It was the spittin image of one of my 6.5x55's I had Ruger put factory sights on. Never bought it tho and it eventually disappeared.

Anyway, if the thing was actually 7x64 might be a winner.

A twist rate check might help, too, as most .280s are slower pitched than the 7x57/7x64.