RSK thanks for the help, but I do use the Norinco Castle nut, this is not the problem. When you slip your F/H over the slotted part of your barrel, the three splines I'm thinking should fit snug in the three slots, there shouldn't be rotational looseness before you start pulling it up tight with the castle nut. Or at least my Norinco original has no rotational play once in the slots. The other american hider worked fine after tightening, or at least it seemed to, but the idea of the ability of the front sight to shirt left or right a fraction of a millimeter was annoying. RTS