The blaster (which you can see in the above image) has a pretty big front end. When it came to bringing the weapon into the world of live-action, Doust and his team wanted to find a reason for it to look the way it does. They actually managed to come up with a pretty creative solution. As Doust explained:
“I had this idea that maybe it’s the fact that as you use a blaster in a gunfight, you pull the trigger, the blaster’s getting hotter and hotter and hotter, eventually it’s not going to work. And with a little flick of the wrist, this whole center section flips over and installs a new cool, cold barrel into the front end of the blaster… It would completely work.”
So not only did they bring a weapon from the expanded universe into live-action, but they managed to improve upon its functionality. This is something that Diego Luna embraced and made use of during the filming of the “Rogue One” prequel. Doust revealed that the actor actually got quite good at utilizing this barrel-switching mechanism.
“Diego [Luna] became really great at flicking the wrist, very subtly hitting the button that controlled the mechanism that spun the barrel. You see him do it a couple of times in some of the scenes, and it’s just this nice little detail.”
And thus, between a video game and some real-world ingenuity, we got Cassian Andor’s blaster.