If you gained 40lbs of muscle in six months I doubt it was the routine.
If you did it doing 5 sets of less that 6 pullups/chinups your a genetic freak.
For overall body mass going heavy enough 5x5 will help, for trying to hit a specific area like the back and increase its size noticebly as fast as possible I don't see that happening.
I think the OP should probably answer everybody's questions before expecting more help.
One more question is what are you looking for width? Thickness? both?