WarIsBoring reports on an exercise that included the shoot down of two small drone targets. Both are recorded in the video above. The first shoot-down is done using a door mounted 7.62mm machinegun like those used in Coast Guard airborne use of force equipped helicopters. The second used a fixed forward firing 20mm gatling gun on an MH-60S (correction applied to the original here).
It seems likely that well financed criminal organizations will soon be using drones to scout ahead of their drug running vessels (if they are not doing it already).
Can we shoot them down?
I wonder if the downwash from the helo might be enough?
Chuck Hill's CG Blog 
I just got some feedback from Benjamin Armstrong, who has experience with the MH-60S and he said the 20mm is fixed and the only gunsight they have is a calibrated Grease pencil mark on the windscreen.
Get that guided .50 cal round going and they could use the M82s that HITRON have been plinking drug boats with.
The .50 cal. sniper rifle might be the best weapon anyway.
Open ocean counter-drone ops might be a good testing ground for developing ways to cope with them in urban settings where collateral damage is a major inhibitor. Rather than shooting them down, devising a method to disable or, better yet, capture them would be preferable. Once we get the laser technology down time to start working on that tractor beam.
That laser weapon may be closer than you think.
http://www.waaytv.com/redstone_alabama/video-boeing-successfully-tests-laser-weapons/article_bc2ae24e-4075-11e5-992c-a36a49205dfd.html
Reportedly a compact system that can take down a UAV can reportedly be carried around by two people.