ButterBolt:  Take your sight off your rifle and soak it in a cup of solvent, like kerosene, denatured alcohol, or Hoppe's #9.  Let it set for a few hours.  You can scrub things around a bit with a toothbrush.  Later, lay the sight on its left side on a small flat piece of hardwood.  Give the lever some light taps with a small plastic headed mallet.  Lever swings to the left to release "binding action".

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