How many on target rounds can you shoot in 3 seconds? I don't care how (or even whether) you carry, loaded, unloaded, cocked or uncocked.
I still don't understand the problem. Why are you 'cocking and locking' an unloaded gun? if you don't want a round in the chamber, don't have one. If you are carrying unloaded, there's no need to apply the safety. The gun can't fire no matter what happens until you rack the slide and load it.