On a 12 bore the striker should protrude to a maximum of .068"/.072" .If they are disc set or loose then there needs to be some end float so I would make them to protrude about .050"/.055" "resting" on the hammers with the provision for them to come out to the full extent of .072" .
If the pins are dragging then it may be that the hammers are not lifting as soon as the gun is started to open , this could be due to ware in any one of several places or if the forend is loose . The cure will depend on the gun and where the ware has occurred .
