Explosives and DR

I could have sworn somewhere that explosives hit the lowest DR of a target but I can’t find it anywhere? Do I roll randomly for location or pick the lowest DR?

As far as I can tell, there’s no special rules for hit locations with Blast weapons. You’d choose a random location just like with any other hit.

I might borrow the “large area injury” rule from GURPS, and use the average DR of the torso and the least-armored location.