Eis has the right idea of it when we're talking about bullets. The shorthand of "caliber" refers to ballistic performance -- speed, energy, penetration, tissue destruction. If you want to rate weapons by a "caliber" system, you're on the right track.
You want your bullet to kill in one hit. It often doesn't. ROF compensates by giving you more chances to hit lethal areas. Burst fire exists as a balance between automatic and semi-automatic fire, giving you additional, more accurate chances to hit.
To @Syaoran's point -- people who are familiar with modern ballistic protection might think that "Class 5 kills Class 5" is a little weird, but it's designed for the sake of players unfamiliar with that system.
That class 5 weapon will kill a class 5 unit if it can hit in lethal spots. A class 4 unit would have to be even more precise, and possibly land more rounds in a single spot. A class 6 weapon will kill a class 5 unit without targeting potentially lethal areas.
You want your bullet to kill in one hit. It often doesn't. ROF compensates by giving you more chances to hit lethal areas. Burst fire exists as a balance between automatic and semi-automatic fire, giving you additional, more accurate chances to hit.
To @Syaoran's point -- people who are familiar with modern ballistic protection might think that "Class 5 kills Class 5" is a little weird, but it's designed for the sake of players unfamiliar with that system.
That class 5 weapon will kill a class 5 unit if it can hit in lethal spots. A class 4 unit would have to be even more precise, and possibly land more rounds in a single spot. A class 6 weapon will kill a class 5 unit without targeting potentially lethal areas.