Just a couple more notes concerning carry up.

One is that the bullet striking the forcing cone will cause the cylinder to center itself with the bore as long as the chamber is within the "confines" of the forcing cone. While the accuracy may be degraded slightly, and leading at the forcing cone increase, it probably won't have much effect on the function of the gun in a Combat role. I have a sneaking hunch that of the original 1917 and Victory revolvers were giving a very thorough check of the stop notches and cylinder stop dimensions that it would be revealed that these War Service guns were built a bit "looser" in this area in the interest of reliability in extreme settings. One byproduct of looser dimensions in these areas is that carryup would be much easier to achieve. It's possible that Ruger uses an increase in the clearance in this area for the same reason, however never having looked closely at a Ruger it's only a possibility.

Another is an observation that is based on a sampling of only 4 revolvers, so it's not in the least bit statistically revelent. However, both of my recently purchased, Lock equipped and MIM using revolvers will pass the "slow motion" test with flying colors as long as the cylinder isn't "dragged" during carryup. On my 610-3 dragging the cylinder will cause it to fail on 2 positions, on my 620 it will carry up perfectly on all 7 unless the drag is extreme and the cylinder is empty. On the other hand my 1988 vintage 67-1 and 1992 vintage 617 will fail occasionally on the slow motion test with an empty cylinder. Note, both of these older guns feature forged internals. I suspect that the use of MIM internals may result in a slight increase in reliability concerning carryup compared to forged due to the decrease in size varations. The simple truth is that the MIM process likely results in a tighter "fit" than the older forged parts allowed.

I've found that there is a rather significant amount of play in the rotation of the extractor star relative to the cylinder in every one of my revolvers. Because of this, I consider the use of fired casings to be an absolute MUST for any carryup test. In an ideal world this should really be done using freshly sized unprimed casings but some of us don't have access to these casings. The simple fact is that play between the extractor and cylinder is reduced when casings are used and in the case of every one of my revolvers that is all that is needed to see the gun carryup perfectly.

Finally, I'm not saying that carryup is not an issue to be concerned about, simply that in many cases some of us may be a bit too critical concerning carryup. That is especially true if you haven't been using fired, or sized and unprimed, casings for this test. Carryup that falls a thou or two short with an unloaded cylinder really isn't something I would be concerned about, in every case I've seen just inserting some empty casings will solve it.