Massad Ayoob defines a tactical reload as "a technique of reloading a partially empty gun in such a way that the shooter maintains control of the remaining live rounds from the first gun-load."
If the gun is only partially empty, then there's a round still in the chamber, and you won't have to worry about the bolt, just eject the partially empty mag and pop in a new one. If you do have to chamber a new round, then the gun is empty, and that's just be a plain old reload.