I've used an ACR for quite a while now to pk with. However, I need to upgrade to a better gun if I want to obtain more player kills and increase my kd ratio.

What I'm looking for includes the following perameters:
At least $20k (nothing over $60k)
Medium ranged efectiveness
Overall PK usefulness
Reload speed quicker than ACR
Increase in overall mobility

Is there any gun that's as close to these perameters as possible?