So, in Fly Casual we get the surface defense blaster cannon, which is a pretty straightforward attachment; a personal scale heavy blaster with it's own integrated gunnery droid brain. I hadn't given it much thought beyond it being pretty much just an inferior, but much cheaper option compared to, say, a vehicle scale auto-blaster with a gunnery droid brain, which costs five times as much but takes up the same number of precious, precious hard points.

But is it though? Vehicle weapons and personal scale weapons work very differently so depending how you interpret the rules these weapons could work be very different.

To sum up:
Vehicle weapons: Difficulty set by comparative Silhouette, range does not matter.
Personal scale weapons: Difficulty set by range, and upgraded by Silhouette.

Now, you can't fit a ground buzzer on a vehicle smaller than Sil 3, so for the purpose of shooting at people your difficulty will get increased at least once either way. The kicker here is that vehicle scale weapons keep increasing the difficulty further with a higher Sil, topping out at a base difficulty of 5 against targets with 4 less Sil. Personal scale weapons only increase it the one time against targets with Sil 2 or more less.

With that in mind, if I've gotten things right, the ground buzzer doesn't really offer any advantages on a Sil 3 vehicle beyond being used at short range (one less difficulty) as a regular vehicle weapon has the same difficulty at medium range and beyond (the ground buzzer is limited to medium range, but even if it wasn't its' accuracy would start decrease beyond that range) and also a vastly superior range and destructive potential. In fact, since you increase the difficulty with autofire, even at short range a vehicle auto-blaster would probably be a mechanically superior choice in most cases as a single shot would deal far more damage than autofire from the ground buzzer. Of course, there is of course such a thing as overkill, but more on that later.

On the other hand, when we get into ships of Sil 4-5 (usually what PCs tend to fart around in), the ground buzzer becomes a more interesting choice as the difficulty to hit Sil 1 targets is going to increase a lot, making it quite useful for clearing out hostile infantry threatening to overrun a ship on the ground (which is is pretty much exactly how such weapons are used in TESB and TFA). Doing this with a vehicle scale weapon is feasible I guess, but at short range from the weapon, the enemy might very well be crawling on the hull of the ship itself or be "danger close" to allies, so less gun might make sense in that case, given how ludicrously destructive vehicle weapons are.

The name "Ground Buzzer" feels a bit misleading though as I get the mental image of a starship "buzzing" the ground and strafing infantry, a task the vehicle scale auto-blaster might be better suited for. On a larger ship the lower difficulty might feel worth it, but ships of that size is probably not your first choice for "buzzing" the ground at the kind of altitude that lets you shoot surface targets at short to medium (personal scale) range.

Did I get this right? Or should you just run the difficulty as for any other vehicle scale weapon?