be new to Revolvers and have just bought a model19-3in really good conditionwith a trigger job allready done. has anyone heard of a spring behind the fireing pin to stop it from swivelling. any info would be appreciated

The Hammer mounted Firing Pins were designed to swivel and must do so to self center. Some of the Smith Hammers have a spring and some don't - both types work equally as well and if yours is the type that is springless - no worries and no need to "fix" cause it ain't broke.