This guide will find out where you can get the Hollowed bullets, Automatic Trigger, and Dual Rounds in Warframe.
Hollowed bullets, Automatic Trigger, and Dual Rounds can all drop from Archwing Interception missions as a rotation reward which you can get on rounds 1,2,5,6, 9, 10, etc.
You can bring just about whatever archwing you want; make sure you’re strong enough to kill the enemies in the mission fairly quickly.
And it shouldn’t be as hard as farming other rare mods since the most common item in the drop pool has a 38% drop chance, and the other mods in the reward pool have the same drop chance as the three mods you are looking for. You shouldn’t have too much trouble getting the mods unless the rng in the game decides otherwise.