If you live in an area where it is ok to shoot in your backyard, and apparently the OP does, let him do it and don't bother him about it. You have to understand that many people choose to live in such a locale for that very reason. If it bothers you that much, move to the city. Then you'll just have to worry about the gang bangers doing the same thing instead of the deputy sheriff.
The fact is that most of us can make a firearm sound full-auto for bursts at a time. It may not be much in the way of practice but it is a hoot from time to time.
Don't forget the fact that he is also a deputy. No, that doesn't give him special standing in any way but even if his firearm is full-auto it may very well be department issued. Swat officers of many agencies maintain their issued full-auto firearms at home and are free to use them at will. In fact, it's generally highly encouraged. I know of a few agencies that issue former military M-16's, still full-auto or tri-burst, to their regular officers. I don't see a problem with that.
As a police officer, I often did not answer the door at my residence. Why, because more than a few times it would be some person out of the blue thinking it was ok to have me help look for their lost dog just because they saw my patrol car in the driveway..... or they wanted to report a vandalism to me while I was still in my underwear rather than making a call to the PD.... or they "just had a question" that they didn't want to bother calling 911 for (apparently they thought it was ok to bother me at all hours instead). Or maybe, just maybe, it was the guy who's life I was being held responsible for ruining and it was payback time.
My advice. Make friends with him. Take over a box of ammo and ask him to shoot it. Learn to love the sound of rights being exercised, or move out of the country to a place where it is nice and quiet.
