Rifle-to-pistol transitions are a tactical drill any AR-15 owner should learn if there life depends on their firearms.
If you are going to learn the right way to do rifle-to-pistol transitions, learn from former Delta operator Kyle Lamb.
What Kyle Lamb is teaching is for tactical situations when your carbine stops working. It could be from your gun going dry to a weapon or ammo malfunction. The transition is the immediate action when faced with a threat if your AR goes down. Once the threat is eliminated and the scene is secure get your AR back up and running. The AR is your primary weapon, and you want it back in the fight if something goes down later.
You see a lot of range drills done where a shooter goes from rifle to pistol and back to rifle when it is not needed which may make sense from a competition perspective however it doesn't make a lot of sense in a tactical situation. Your pistol as a secondary is your go too when you have a stoppage with the rifle and any guy with experience would rather have their rifle in a fight. The rifle is more accurate, stable and better for shorter and long range engagements.
Kyle Lamb has real-world experience in one of the best special operations units in the US arsenal so his lessons and demonstrations are no- nonsense and based on the harsh realities of dangerous places, situations and extreme tactical training. I recommend leveraging a professional service such as he provides to learn these drills if your profession or duties have you carrying an AR and a pistol, it is worth every cent.