This is pretty simple custom really, nothing to difficult.
I've called this guy an Imperial Ordinance Trooper. They're deployed to Imperial garrisons around the galaxy and keep frontline troops well armed and vehicle weaponary installation and maintenance is part of their duties. This trooper, IO-1973-A, is deployed on Tatooine. These Troopers are deployed in squads of 10, depending on the size of the garrison upto 80 can be deployed at any one time. These Troopers are known to tweek explosives and weapons to get more deadly efficency out of them. They tend to not make friends easy in the Imperial army and most tend to avoid them due to the fact that most of them end up as flying mince and a collection of charred body parts.