How many rounds are in your mags during the drill? And it depends on the situation. Some situations are better to switch to the secondary even your primary has a round in it. Not safe bust sometimes necessary.
If anyone is interested, the AMU/CMP put out a Video on "Close Quarters Marksmanship" transitioning from rifle to pistol that's rather good, if anyone is considering Multi-gun or Three Gun matches.
Covers Kit Set Up, 7 Principles of High Performance Shooting, Weapons Presentation, Accuracy, Targets, The Reload, The Mental Game, Range Drills, The Ready Up Drill, Recoil Management, Multiple Threat Engagements, Shooting on the Move, Changing Gears Drills, Alternate Position, Weapons
Transition & Malfunctions.