The rounds must be assumed to be live, as the failure to ignite could simply be caused by a firing pin that was a trifle short or slowed down by crud, or a chamber with excessive headspace, so that the case was pushed forwards rather than struck firmly. It is therefore gravely irresponsible (and may even be a criminal offence, depending on where you live) to discard such ammo. In another rifle, with a slightly harder strike, or a firing pin that is a gnat's whicker longer, those rounds might fire.