You need to fire below its rate of fire. They added a system that reduces the accuracy of shots when you fire hand cannon at max rate so waiting a tiny amount after each shot helps a lot. Aim for the head don't get in the dot killing them. Hand cannons, excluding the last word have rather long time to time team that with the accuracy system I mentioned above you have a hard time. However that said you can be very very ready with hand cannons if you have smooth chilled play style. Straying from side to side and making each shot hit is what counts.