At one time the US army was apparently concerned with the problem of a failure to fire and wanted to have a feature on a weapon to give the primer a second blow. That's why Springfield bolt actions have a cocking piece, which I think is unique among Mauser actions. A few other non-Mauser designs have that feature but probably not for the same reason. A 1911 has that feature as well, though no revolvers have it. I expect the reasoning behind the feature is to hopefully avoid the possibility of a late ignition happening after the bolt was open.