Your project is going well. The gun is now mechanically sound, but it is simply a gun: it has no intrinsic power of its own. You'll need to reconnect it to the Light somehow, and the vast dark secrets of the Void seem like the most promising route. Defeat Guardians in the Crucible using Void energy or Hand Cannons. Precision streaks using Void Hand Cannons grant the most efficient progress. Note that progress is multiplied in the Iron Banner or in Survival Crucible matches.