Some issues about the concept.
I had seen it already on DEFENSEREVIEW, an unmanned-automated remote-controlled flying device armed with a light automatic weapon is a nice (and a bit futuristic) concept for short-range recon, engaging of small enemy units, and area-denial and area-patrol/defense operations (think about an high-security perimeter like a nuclear power plant or a secret experiment center stranded in the middle of nowhere that's patrolled by these little cute bots...).
But the concept poses some problems.
#1: At the current state, the bots (if we can call them such) need to be remote-controlled by a human operator. Can the operator always be at range to ensure proper control of the bots? (Read: does the remote control system ranges enough to prevent the bots that are, for example, in pursuit of an escaping enemy Sapper team, to go out of range and crash? A big problem since the enemy could capture an almost-intact one and take it back to their Intel to worm its secrets out). Plus: does every single bot requires an individual operator? If yes, this is another problem to face (imagine a testing ground that has a wide perimeter to be guarded, this calls for some dozens of bots, and THIS calls for a control room with dozens of operators). Can the bot(s) all toegether be controlled by a computer? If yes, do we already have (and if not, in how much time can we achieve) a computer with enough A.I. to control these drones? And how do we deal with the fact that they may mistake a friend or a stranded civilian for an intruder or an enemy and slaughter him?
#2: At the current state, these drones are "weaponized" with a weapon that has 12-rounds clips or 20-rounds drum magazines. Now, imagine if all the drones patrolling a certain high-stack area are required to direct towards the main gate, that's just been crushed by a Kamikaze tank truck full of explosive like happened to the Italian base in Nassiriya in November 2003, and take it out before it is sent to crash against the main installation. For a drone that might be tasked with such an operation, the capacity given today by the employed technology is WAY too little; we are talking about something that might be required to unload HUNDREDS of rounds against a wide, moving target that has lots of inertia on its side, and stop it before it is too late. With 20 12-gauge rounds? Not even if them are explosive shells! When 19 Italians died on such an attack to the Italian "Maestrale" ("Mistral") base in Nassiriya, on 11/12/2003, what theguard soldiers actually did was to shoot dead the truck driver when it crushed the gate. This didn't stopped the vehicle: lots of speed when it arrived, lots of mass, equal lots of inertia. Tho accomplish such a task, the drones need MUCH more powerful weapon than a 12-gauge. My suggestion would be a specifically-designed, belt-fed machinegun chambered for something like 300 - Winchester Magnum or 338 - Lapua Magnum. The machinegun should be a 3-rotating-barrelled, Gatling-operated system with a feeding belt housed in a container that allows every single drone to carry from 600 up to 5000 rounds per time. I know that is weight added to the structure and would prevent it from flying, and that we have to calculate the effect of the recoil on the flight of the drone, but we have to find a solution to this problem, if we don't want to find ourselves crossing our fingers and hoping for the best when such an armed drone will be the only thing standing between a nuclear power plant and a tank truck filled with explosive launched at 100 MpH.
If the drone is instead used only as an anti-personnel surveillance system, then the solution would be a small automatic weapon firing pistol-caliber ammunitions (.9x19mm, .40-S&W, .45-ACP, or even something more powerful and punchie like .10mm-Auto or revolver cartridges: .357-Magnum, .44-Magnum, .30-Carbine...), or some HV rounds like .5'7x28mm-FN or .4'6x30mm-HK, or even .5'56x45mm-NATO: small calibers that would allow a HUGE ammunitions capacity and enough punch to bring down a dismounted human enemy target. The 12-gauge cannon as prototyped today would be good too, but the ammunitions capacity issue remains unsolved then.
Ammunitions capacity is important also because, remember, when the drone runs out of ammo it must be called back to base for reloading, and sometimes you just can NOT allow yourself to have one less gun out there.
#3: Fuel distance. What if a group of such drones is sent after an enemy patrol that has, let's say, gathered some Intel informations that must NOT end up in the hands of their commanders, or if them are sent in a medium-to-long-distance recon operation to locate hiding/approaching enemy units or traps along the way for an incoming ground force? A simple fuel tank is not enough.
Any possible response to such problems? You might say that such questions are "pointless" since the use of this drone, as conceived today, is for very short range operations and that it is "weaponized" for pure self-defense. But the use of such drones in actual security/recon operations is around the corner as for technology capabilities, and taking the opportunity today would mean to save a lot of lives in the near future.
"It is criminal to teach a man not to defend himself, when he is the constant victim of brutal attacks. It is legal and lawful to own a shotgun or a rifle. We believe in obeying the law." -- Malcolm X
"We (atheists) act in good conscience because we believe in moral principles, not because we expect a reward in Heaven." -- Margherita Hack