Had no effect on pressure - Luth-AR AR-15 Adjustable Gas Block .750 ID

Replaced my standard gas block with this adjustable one to tone down the gas pressure on a slightly over gassed AR15. It seemed to make absolutely no difference regardless of how the screw was adjusted. Started with the screw as far into the block as it would go with the expectation of short stroking. This was not the case though, it seemed no different than my standard gas block. Backed the screw out all the way, no change. Tried every increment in between and still no change. My hunch is that the adjustment screw cannot actually go far enough in to block gas flow, but who knows. Unable to return since I have already installed it. Very disappointing.