Better yet, replace a sentry with an Area Denial Weapons System otherwise known as the MetalStorm.
My father helped to develop this during his time working for the ADI.
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Yes and no, I have seen a motion tracker one.
The machine gun is placed on an area that nobody is allowed in, the robot can move in around 360 degree with cameras all around, it can change into three mode: Normal, infrared, and night. The camera automatically lock the gun at the target and will fire, once the gun is fired, a computer specialist can see the gun via computer and see what the camera see.
However, I didn't mean to say it is outdated what you showed me, I said it looks outdated. But I can be easily proven wrong.
I assume you are talking about the FireStorm (or a similar system) which is developed by the same company and licensed through the ADI.
Metal Storm - Unmanned Systems/Robotic Platforms
But its a different system all together. Area denial systems like the MetalStorm which is the companies (also called MetalStorm) flagship system, are meant to replace defensive setups such as minefields and are only aftive if the perimeter has been breeched. Unlike minefields the motion sensors are discriminant and be override by an external controller to ensure the safety of friendlies and civilians.
Love the Cornershot.
On topic: the closest you can get is the AA-12 which fires 300 rounds per minute from memory. Or the USAS-12 which fires at around 425 rounds per minute.
My fathers has collectively served over 30 years in the military, air force and as a contractor at ADI (Australian Defence Institute). My uncle has served 15 years in the military, and was present in Somalia during the civil war.