My favorite "no-drill" Krag peep sight is the Redfield 102-K.  It requires no removal of wood.  Loosening the coin-slotted side lock screw, allows the slide to be pulled up enough to allow bolt removal for cleaning.  The elevation set screw allows slide to be returned to sighted in position (if the set screw was utilized properly).  The Redfields do require a cut-off shaped shaft to fill the magazine cut-off hole for smooth magazine feeding.  The Redfield 70K micrometer versions look nice, but it is probably quicker to remove the sight from the action, than the slide from its base.

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