Originally Posted by outkast kid
Yes, that's actually just the air pressure changing from the internals moving. If that hole weren't there the piston would be impeded because it would be trying to move in an air-tight space. As long as you only feel it when the reg cycles then it's perfectly normal.
what he said. same reason theres a hole in the LPR cap. BTW, don't cover that hole
If it's leaking constantly, relube the piston oring.