I have used a level 28 Longbow Pandemic clear through level 42 before I was finally able to replace it.
I pray I get a high level version although I know the chances are VERY tiny.
I think pandemic is already the best legendary grenade mod in the game without debate, and it gaining the "longbow" ability was just random luck that made it like 100x better. --- From this day forward, I will troll no more forever. 17 JAN 2012