Mystery DAN WESSON Revolver set screw

[Bitter Clinger]

This set screw reportedly fell out of the hammer cavity of my BIL's Dan Wesson revolver. Anyone recognize or happen to know what it's purpose might have been? He said that gun was running fine but then hammer would not cock after firing many rounds. Once screw fell out, trigger action seemed to have "improved". We looked online but there appear to be no legible diagrams out there for a gun of this vintage:

[Archery1]

Looks like it is the cylinder aligning ball cap screw. Top spring, ball, and screw in attached pic and located right where your pictured one came from.

[mrvmax]

You may find a diagram here: http://www.gunpartscorp.com/Manufacture ... -33200.htm

[Archery1]

You may find a diagram here: http://www.gunpartscorp.com/Manufacture ... -33200.htm

Great source! Not that a new screw is needed, but here it is identified from that source: http://www.gunpartscorp.com/Products/155500A.htm

[Bitter Clinger]

Thank you Gentlemen! Your expertise is appreciated!

[FL450]

From my Dan Wesson