What should you do first to perform a transition to a handgun drill with a 3-point tactical sling?

The first step to performing a transition to a handgun drill with a 3-point tactical sling is to ensure that the rifle is placed on Safe. This critical action promotes safety by preventing an accidental discharge while transitioning to the handgun. Ensuring the weapon is safe allows the operator to focus on the mechanics of the transition without the added concern of handling a firearm that is not secured.

Other actions, such as checking the magazine or removing the sling, can be relevant but come after confirming the rifle's safety status. Dropping the rifle also poses safety risks and does not align with proper firearm handling protocols. Thus, making the rifle safe is the essential first step in this drill.