Could you hit a moving drone with a rifle? Even when I shot competitively at 500m, I probably couldn't. You can hit clay pigeons with a shotgun but a drone can easily manoeuvre beyond range.

A perimeter defense would need to be established, with radars for long range scanning. And cameras for short range confirmation. It will also need infrared cameras to operate at night.

A computer system would monitor the perimeter, for all incoming threats. This computer system must be very powerful, as it is processing a lot of data in real time. However, this kind of technology should now be in the realms of deep learning AI that is currently being developed now.

Once a positive visual confirmation is made, to determine that the aerial object is an intrusion drone, then an alert can be given to the human commander, of the incoming threat. And a human can still stay in the loop to order the execution.

Then, a turret mounted laser cannon, can be used to burn down the drone. Or even a rifle can be used to kill the drone with a kinetic impact. The accuracy of a bullet fired by a robot, should far exceed the skill of the best human sniper. But bullets still follow a parabolic path, so a turret mounted laser cannon is more flexible to destroy drones.