Firing pin protrusion is measured by first swinging the cylinder out then pushing the release button forward and cock the hammer. Push the firing pin fully forward with a tool then using gap gauge blades stacked on the recoil shield where they equal the same thickness as the tip of the firing pin. This is not an absolute number but rather a range from .035" to .045" for all Ruger revolvers (except rimfires). Make sure you push against the firing pin and not the transfer bar..
Tnx for response. It's appreciated.fjlee, Knowing how you like to "make" things, I thought I would post a pic of an Ordnance Firing Pin Protrusion gauge I picked up in a salvage yard back in the 70's. I'll bet you already figured out where this is going! ....................Dick