I've seen these with thread locker or something like it in them (to tighten a wobble?) and a little heat will loosen it right up. They must be tight or the sight will be a slight bit loose. Have you tried freezing the thing yet. Feezing the gun in a home freezer compartment will shrink the blade slightly and also widen the slot, creating a bit of looseness. Protect the blade with brass on the jaws holding it to avoid marring..
