how to make procedure "when entity swings item" not just in air, but could on block or entity?

I want to create a gun that can shoot with just a left-click. I know I could make it a "ranged item" to achieve this, but that would only allow the gun to shoot with a right-click, which is not what I want. Currently, I've successfully created a gun using the "when entity swings item" procedure to enable left-click shooting, but this only works when the item is swung in the air. If I focus on a block or an entity, it fails.

Can anyone help me with this issue? Or is there another way to make a "left-click only" gun? Thank you!