On one hand I get it, the nostalgia element of him always having a gun. I chalk that up to the time he came out there were a few hardcore, badass guys with guns thing. I do think that a point can be made for him to do away with the gun if only to show the evolution of his character and powers. Bishop has better fine control over his power to the point where he is tougher to injure and has small healing factor due to diverting excess energy that he's absorbed.
I’m down with dropping the guns for Bishop and all mutants. Guns are products of human violence. Mutants can do better.
Bishop has some big guns on his arms! he doesn't need another