Bob,
Model 70's will fail to fire if the bolt is lifted slightly.
There's also a combination where a slightly lifted bolt with the safety in the middle position (where many hunters put it when expecting action any moment) will lock the safety, so it can't be pushed forward. Apparently this can can happen with "Classics," and was part of a well-known Cape buffalo run-in a few years ago where a hunter got severely injured, partly because the safety on one of the other hunters' Model 70 would not go forward. (However, I have not been able to reproduce this condition with a pre-'64, though I've only tried it on three.)
