Gramma Cleric on Semi-Auto with (SoaG Lv3) and (SoaB Lv3) with (Trigger Happy Lv1) does about:
((3 to 24)+3+3) * (3+1)
=
(6 to 30) * (4)
=
about (24 to 120!)
per salvo, I should think. Someone correct me if my calcs are inaccurate, please.
I was able to put something like this to the test in one of my runs in 'normal' difficulty, I can just about gun down an Arachnotron without reloading.