The cornerstone of all biathletes for indoor training is aim shooting training.
What is exactly going on?
Aim shooting training is a practice and memorizing of the shooting workflow.
The biathlete comes to the “shooting line” in front of targets (at least black dot on the wall) and starts the whole workflow of shooting (of course without loading the weapon) and aiming. He has to pay attention to all details connected to the shooting.
My advice is to lock the trigger to protect the firing pin.