It's a Long action, which used to be "standard" but is no longer. The .243 - .308 is called a Medium action, or Short. The Ruger M77 is a mauser-type action, so you need Long.
That's one of the reasons why the 7x57 is moribund. You can get 7 x 64 in the same Long action (not from Ruger) with more zip.... and the same zip is on tap for the 7mm-08 in Medium or Short.
If the 7x57 had been chambered in LH & RH then more buyers would have considered it ... but at least 1 out of every 6 rifle-shooters now won't even consider it as an option.