[2019] What's up with Merciless's Guerrilla Warfare talent?

When you pull the trigger, it shoots a primer, when you release the trigger it detonates. It says you can have up to 5 primers on a target but it only shoots 1 bullet at a time and you have to release the trigger to shoot another one so how am I suppose to put 5 primers on a target? Am I missing something? Is there a way to shoot more than 1 bullet without releasing the trigger?