How Does Sponsored By Work?

Say I was using an Absolute Zero laser with a torgue buff from a Nukem. Would the bonus explosive damage be 25% of the current weapon in my hands (aka the AZ), or 25% of the explosive gun’s damage (aka the nukem)? Because it could be super powerful as the nukem has one of the highest base damages in the game.

Your weapon, not the weapon you switch from. 25% of ~500K from a Derp Duurp would be ridiculous.