If you want to swap to another cam, one way is doing it in your level blueprint via an event and the node “Set View Target With Blend”, that will allow the camera to transition from your character camera to the actor camera rather than switch right to it. Could add a nice effect to the bullet cam, that it blends over to it. You can also adjust the blend in that node to make it instant.
As for the event triggering it, you want the bullet camera active when the bullet is set to hit the enemy, correct? That could be a bit more tricky, like a line trace or something so you know it will hit, but it CAN technically still miss with movement… unlikely in a singleplayer though.