I already have a zastava m70 in 9.3x62, and original mauser action from older sporters, also the newer win m70 control feed, but I was also looking to have the ruger m77 mauser pattern action. So I guess ill pass on the one I mentioned above and look out for the mkII or newer.
Don't be so quick to pass on that rifle.
Ruger was going through some changes at the time you mention but still weren't making their own barrels yet. They had several suppliers, usually based on cost, rather than performance.
The post about the 7x57 is misleading. It may have come from experience and a comment made by Dave Scovill.
I recently sold a Ruger MkI in 7x57 and it was an acceptable shooter with factory ammo. Two inch groups were the norm. I could tighten the groups up to MOA with hand loads and specific weight bullets. Anything under 139 grains didn't shoot well at all.
I have a MKII for sale, chambered in 220 Swift. It shoots better than I can hold it.
On the other hand, I have had Ruger bolt actions that would shoot shotgun sized groups regularly. I believe this hit and miss problem really got bad after old Bill Ruger lost control of the company, to his son and BODs just before he passed on. Their quality control was minimal at best and their manufacturing equipment/tooling was wearing out.
To my knowledge, the MKII model 77s are all manufactured on CNC machinery and Ruger produced barrels are exclusively installed.
Take that rifle out and shoot it before you buy it. If the seller refuses to allow this, then back away. Proof is in the shooting.