How do you deal damage with the peacekeeper?

The pk came up in gun run tonight, it was a very bad cheater lobby, so I had to sneak around to get kills.  The pk was the third gun, so I was stuck on that gun since it did 9 damage when my opponents always downed me with 1 or 2 hits.  

I haven't used the pk in awhile, but I remember it doing a lot more damage than that at one time.  Was the low damage because I was hitting cheaters that had a script to reduce their damage or is there a way to fire the pk and actually do some damage?  I was able to use the R301 and Hemlock just fine in the gun run and I was able to move fast enough to avoid a one shot, but the pk just doesn't do enough damage to kill an opponent like that, and during reload I just get one shotted.

Is it rng how much damage it does and I just got a bad luck streak, or can you get closer to the opponent and squeeze off a few shots to maybe get a kill?  I thought maybe the circle getting smaller on the reticle was the secret, but I tried it with the circle closed and open and the damage was still 9.

Any help or tips would be appreciated if this gun comes up in gun run again?  Gun run is my favorite mixtape mode now when it has legit players since it gives me a chance to warmup on every gun, and I'd hate to have to stop because I can't use one gun.  The sniper weapons are a problem too in gun run, but they at least do huge damage when you land a shot.