The VSR-10 hop up adjustment arm is intrinsically flawed by using a slider that can budget out of place. I replaced mine with a screw on top (which allowed me to push the arm further down for more hop on heavy BBs), check this out.
Top Dead Center Hop-up Mod - VSR10/BAR10/MB03/MB07
Top Dead Center Hop-up Mod - VSR10/BAR10/MB03/MB07
