Try to expose the sights before shooting to the stronger light source for longer time ( 10 minutes or more ). Sights dots are made out of phospor and therefore they need a time to consume the light to be bright in a dark. Usualy the gun is placed in such places ( holster under the jacket, tresor, gun box ) which prevents light from charging the dots. So suitable exposure to the light should correct his problem. However just for time they fire accumulated light out and then "re-charging" is needed. There are also tritium sight available from other sources which has not this drawback, because tritium is "radio-active" element shining its own internal energy.
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