Go to the Ruger website, under customer service, historical data, rifles, select your model, find serial number, and it will show year of manufacture.
If the Ruger website is up, it has sn data.
Ruger's website has extensive sn data.
100-500
Depending on condition, and WHICH version of the M77, between $250 and $500.
Unknown caliber. Contact Ruger
The Ruger website, under customer service, historical data, rifle, M77, will have the serial number ranges for each year of production.
Remington 700 308?
50-700 usd
Long
100-400
Strong enough for factory loaded ammunition and hand loads that don't exceed SAMMI standards.
Request an owner's manual from Ruger on their web site or take it to a gun smith.