I don't see how, using my system (rough stats of what I think would be suitable)

PBP = 5 damage upgraded
First bullet = 5 damage
Second = 2
Third = 4
fourth = 2

13 damage if all bullets hit :o
Gotta remember if it does unbalance the 125k weapon, we can modify the system to work better with it (Or if we did 0.5 damage, it could actually make the entire damamge system one hundred times easier xD)
or change the guns stats to meet the new requirements.

Basically, we can all agree the PBP is pretty overkill at this point with a 3 hit kill more times than not.

Alternative being we just leave the PBP how it is haha, i'm just offering up alternatives that people may like to try to see if it helps balance the game any better Since i'm sure there will be more shotguns in future it would be beneficial in the long run.