Hmmm...51 Navy C&B ... the screw is there to retain the spring catch , when the wedge is tapped out.
You do not turn it to release the wedge , just tap the wedge through and allow the screw to catch the spring stop.
when re-installing the barrel wedge on your 51 Navy C&B the spring catch just should just clear the lug allowing it to retain the
wedge ...unlike the 51 R&M which has a flat on the screw and no spring on the wedge and is turned to allow the wedge to remove.....
if you look closely the 51 C&B Navy screw head is round, the Navy 51 R&M Conversion has a D shaped head, that is the flat of which I'm mentioning.