Ed,
Made me look didn't cha? I dug my Blackhawk and my Virgina Dragoon out of the safe just to verify it. The .44 mag Dragoon is a "traditional" 4 stop S/A, where the "clicks" line up a chamber. The deep part of the cut out for the bolt stop on the Dragoon is more over the thin part of the chamber. The only reason the Dragoon can stand up to this( .44mag pressures) as opposed to a Colt SAA, is because it's roughly 1/3 larger than a SAA.
The prawl and the bolt stop work in congunction to hold the cylinder in battery. With the offset on the Dragoon being further to the clockwise, that means the prawl is just a smidgen shorter, hence at half cock (loading), it puts a chamber just to the left of center. On the Blackhawk (same arrangement as a Vaquero)the longer prawl pushes the chamber more to the clockwise, and the chamber goes past center.
Then there's also the difference in the cylinder "star" where the prawl catches. The Dragoon (and my 1851 Navy BTW-another 4 click) have smaller hands which engage in a taper fashion, where the Ruger uses a squared arrangement. The Ruger uses a massive squared arrangement and a small bolt stop to hold the cylinder in battery. The Dragoon uses the reverse. A massive bolt stop and a small prawl. Combine the bolt stop cut out placement with the squared prawl in the unlocking arrangement Ruger uses, and the cylinder is just a smidge out of center.
It's hard to describe without having the 2 side by side. Here's a couple of pictures that might help. The Dragoon cylinder is on the left and the Ruger is on the right. Kinda hard to see, but the Dragoon bolt sopt cutout is about twice as wide. The 1851 Colt Navy is about the same as the Dragoon. While I don't have a real Colt SAA, I'm fairly certain it's built like the Dragoon and the Navy.('scuse the fuzzy image,,,it's early and I've only had one cup o' Joe
)