This is a great video that touches on what you have to do to legally convert a Glock or other pistol into an SBR and also covers a bit of the benefits and drawbacks of the process.
I’m of two minds about it. While it’s true you can put multiple shots on the same target very quickly, because you have to hold your torso in a very rigid position, it’s slower to transition between multiple targets. That’s in addition to making manipulating the controls more difficult.
It also changes the way you use the sights, after all, they’re handgun sights, not rifle sights.
But it’s extremely nice for when you’ve got a gun that really kicks, like a Glock 22 or 24 chambered in .40 S&W, which tend to be snappy to the point where many people would just rather not. And it lets you put a pistol grip on the dust cover, which is actually pretty nice.