Just read and criticize afterwards.

-15% slower fire rate
+10% faster reload speed
-20% damage penalty
One random shot is a guaranteed crit in every clip.
After crit, 4 seconds of 20% increased damage vulnerability.

Taunt kill: Heavy inserts a shell, lifts the gun, says random quote of the following:

" I am Heavy weapons guy, and this is my new weapon!"
"Did you think you could beat me?"
"You are dead, not big surprise."
"I will kill you, and kill you, and kill you!"

Fires after quote is finished and says "POW, ha ha!"