RE: rem 7400?
I had a Rem 742 and then 7400 (slightly updated version of the former). I' d say that for both, the most important thing I' ve found to keep it operating well is to keep the bolt and chamber clean, clean, clean and use very little of a high-quality lubrication. This is especially true in cold weather ( 10 degress of lower).
I think that their manufacturing tolerances and the bolt locking mechanism are 2 reasons why many people end up with 1 shot, manual ejection of the spent casing or manual setting of the live round.
With my latest high-power rifle purchase, I' ve gone to a Tikka bolt-action. I know that it' ll hit what I aim at and it' s up to me to eject and load another round, if need be.
MinnFinn