In March 2015 I bought two Ruger New Vaqueros, practically identical except for serial numbers, for Milady and I to shoot in CFDA competition and practice. I was not unfamiliar with the single-action platform, having owned a couple of Super Blackhawks over the years. They worked as advertised, just like they were supposed to. Over the intervening year, I've learned more about the New Vaquero and the seeming differences between the New Vaquero and the (old) Vaquero.
For example. The New Vaquero is more svelte than the old. It's built on a smaller frame, to more closely match the size of the Colt Model P. Recently, though, I had a buddy who shoots Rugers have a malfunction that we traced to the reverse index plunger, which stops the cylinder from spinning in both directions. It's a small, spring loaded plunger that stops the cylinder from spinning backwards. In the below diagram, it's part numbers 32, 33, and 34.
Of course, you can click on the picture for a larger image. Some of the Cowboy Action shooters remove that indexing plunger so that the cylinder will spin backwards. They have some shoots where quick reloads and backwards indexing is a benefit, so they take out the indexing plunger. Here's a picture of the indexing plunger. Look at the plunger inside the red circle, just under the base pin.
I was looking at my Old Vaquero, made in 1993, the other night and took the cylinder out. The Old Vaquero doesn't have the indexing plunger. The cylinder is prevented from backwards rotation by the spring tension on the pawl. Of course, some industrious cowboys have figured out a mod to allow reverse indexing on the old revolvers. But, in CFDA, that mod is specifically disallowed. Here's a picture of the recoil shield on that revolver. With the red circle where the indexing plunger should be.
It's interesting to look at the design differences between the models. In both of my Old models, the base-pin is captured. You would have to remove the ejector rod to fully remove the base pin. In the New models, the base pin comes fully away from the gun. In the Old Models, we don't find the indexing plunger, but we find them in the New models.
Ruger is not finished making changes. I've learned that this year's models have a new transfer bar. They've identified some type of problem and made engineering changes to the revolver as they've gone along. I don't have a problem with that at all, but it helps to know not only which model you have, but when the engineering changes occurred.
It's all part of the fun.