Don't think Ruger ever used Douglas barrels, too expensive. In fact most comments are to the contrary complaining about hit and miss quality and accuracy of M77 barrels. My gunsmith who is a fan of M77's says most of the accuracy issues are with the trigger.
Got mine Christmas 1969/70. Gun Smith where purchased did trigger and putWeaver K-6x scope on it. I shot 130gr Speer BT/Sp over 48.5 gr IMR 4895
same as my dad shot in Win 70. Rifle is tack driver. I would not buy a new
model, quality is down like every thing else. I have herd they used Doughlas
barrels back then,but haven't been able to verify that. If my old gun smith
was still kicking he would know. He was in WVa and was a good customer of
theirs. I have a 243 on 98 and 22 wildcat on Martini with Doughlas barrels.
At one time I had 7 custom rifles on 98s or pre 64 m70s, from 222 to 375H&H
all with Doughlas barrels. All were accurate rifles. Wish I hadn't traded them