I had a M77 7 mag once that failed to fire on the first two deer I shot at on cold mornings. It would fire when I got back home later. The problem was the firing pin spring was dragging on the bolt. I got a new spring and the problem was solved.
That reminds me that my hunting buddy's M77 failed 2-3 years in a row in the field. It worked fine at the range but when we got in the field it would go 'click'. After each experience I suggested he replace the firing pin spring. When he finally did the old spring was a couple inches shorter than the replacement. Turns out he had been storing the rifle with the spring compressed, even though I had shown him more than once how to release the spring by holding the trigger back while closing the bolt.
I don't blame the rifle as much as the storage method.
