Yes, this is a fun job. Yes, you should be jealous at times. (Only at times, the rest of the time it is work. Trust me.) I recently had an afternoon with a full-auto toy par exellance: a converted Glock 17.
I know what you're thinking: "Oh god, would that be the world's best zombie-slayer? I would rule the world." Alas, no you wouldn't. At 1,000 rpm, it went through ammo at an eye-blinking rate. I could control it, but I am me. Not to get all bragging and such, but I've been at this a long time, I've shot a lot of ammo and I know how to control recoil. There were other shooters along, and at times I feared for the range signs up on top of the berms. A five-shot burst that spans eight feet, from lowest to highest shot, at seven yards? That is going to slay zombies?
Could I get a head shot out of a burst at regular distances? Sure, but why do it quickly with five rounds when I could do it in plenty of time with one? Ammo is heavy, and ought not to be wasted.
As part of the testing, I ran an impromptu practical stage. As designed, it required 23 rounds, and took most of the competitors about 20 seconds or so. The faster guys did it in the mid-teens. On auto, it took me 28 seconds (OK, there was a malfunction) and more than 23 rounds to finish.
Fun? You bet. But not as fast as I could have done the stage, shooting single head shots with the Glock on semi, and with a lot less ammo expended.
And remember, head shots rule. A whole 33-round magazine, hosed at full speed through the legs of the assembled shufflers, isn't going to do you any good. Now, a mag, controlled, dumped into a fast-mover, that might be useful.
So, if in scrounging through the local PD, post-apocalypse, you come across a G-18, cool. Just don't expect more from the giggle switch than entertainment. Depending on full-auto fire, when it wasn't warranted, may be exactly what got its previous owner's brains munched.