I admit I prefer blimp drones with whatever shoots furthest. Add a silencer, your usual no-see-ums, and keep it up there more-or-less indefinitely. If the rigger is particularly clever and has a little bit more cash (or is building up his store), get multiple drones, acquire storage locations in each district as launch points, put the drones in there, and if you have to race from Puyallup to Auburn, well, you'll still have a friend in the sky when you get there.
Are the Barrett rounds still a billion bucks a pop? I would presume so, but I'll confess to not being as up on the dirty details as I absolutely used to be...