I have one from about 1978 and it developed a similar problem in February right before my South Carolina pig hunt. I sprayed carb cleaner into the action down and it functioned for a few rounds when I tested it, but then mis-fired when I had a 200 pound boar at 100 yards - go figure. When I got back I took it to a gunsmith I trust and he put the action in a sonic cleaner with solvent and said all manner of sand came out of the firing pin assembly. I guess all those antelope and elk hunting trips finally got enough dirt into places where you can't get to it without dis-assembly and that it just blocked the firing pin and ceased to fire.
So my advice is to either disassemble the action and give it a thorough cleaning or take it to a competent gunsmith to do it for you.
I have killed an antelope at 1006 yards with it so accuracy is pretty good.
As far as the pig hunting went the guys came down from Bragg and got a small one so we were not skunked. They took it back and grilled it outside the barracks. Funny thing was at the end of Robin Sage a pick up truck rolls up with a pig in the back for them to kill, clean and BBQ so they knew what to do with a pig.
P.S. The late 70's have an adjustable trigger that is easily as good as any trigger on the market now.
The man in black fled across the desert, and the gunslinger followed.