Would you use the Single shot in the Cane-Gun to shoot the person(s) who set the timer Collar Bomb on your neck. The one person that could diffuse it or stop the detonation.
I wouldn't
I think the Cane-Gun was given him to potentially be a more effective robber.
Why make and disguise a weapon? What's he going to do - tell the teller "give me the money or I'll shoot you with my cane"? Why not give him an empty gun or make something that looks like a gun? Why give him a gun at all if he isn't going to shoot anyone?
None of this makes sense.