Texas John Ringo,
You are correct sir, and I stand corrected.
I ran by my shop at lunch and looked at 4 different Colt's pattern "open top" pistols that are germane to this discussion. I looked at a Uberti Type 2 "conversion," a Uberti Open Top, an ASM Type 1 "conversion" and a Uberti Army model I am using as the base for a true conversion to .44 Colt. The last one still has a single stage hand and it still doesn't engage the ratchet even though it now sticks much further forward and at a different engagement angle with the new recoil shield added.
I read both Coffinmaker's and Pettifogger's comments, but I can't see how they apply (of course I have been wrong before). It is true the gas shields on the Uberti pistols control the minimum cylinder gap, but the maximum we are usually concerned with is still controlled by the bearing face at the rear of the cylinder as it is pushed to the rear.
So for measurement purposes with a cartridge revolver of the type we are talking about I believe (after being enlightened by Ringo) that the gap is best measured with the hammer down, or with the innards out of the revolver. For Cap and Ball revolvers the directions I originally posted for Santee apply because the hammer either sits on the cone or prevents the cylinder from moving back to the bearing face.
What you posted made sense Ringo, so I checked. I also looked at a S.A.A., a '58 reproduction and a modern S&W and Colt D.A. revolver as well. The measurement with the hammer back applies to C&B pistols. There may be some other varieties that have hand pressure with the hammer down, but for our purposes and addressing what Santee asked about (remember this is the STORM board) I'm going to say cartridge pistols should be measured with the hammer down.
I know Pettifogger and Coffinmaker have considerable experience, perhaps they have seen a set-up that will be influenced by the hammer on a "conversion," I can't speak beyond what I have researched, modeled ,built or own. They will have to address that.
So Santee, get someone to help you hold the revolver or hold it in a fixture or vise to allow you to use both hands in fitting those strips of paper. Don't cock it all because as soon as you move the hammer back the hand moves up and forward. It still may not even be touching the cylinder at half cock, but why even potentially bring it into play?
Best regards to you Ringo,
Mako