You do not understand or have not encountered the “New and Improved” Williams receiver sight.
It is not really Williams fault. Marlin quit drilling their rifles for the sight and Williams changed the mount to use the scope mount screw holes.
Ken K posted this picture of his sight and it is better than mine.
The sight base now uses the scope mount screw holes.
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The new Williams sight base causes the sight to hang off rear of the receiver.
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This causes the sight to interfier with the thumb cocking the hammer.
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Slim