Tuning Revolver-Cylinder Lockup

By the term "old-style two-point lockup," I’m referring to a design first used by Smith & Wesson in the early 1900s. In this design, the cylinder locked into the frame at two points’t he tip of the ejector rod in the underlug and at the rear in the center-pin opening in the recoil shield. This type of lockup has been used on other revolvers as well, namely, Astra, Llama, Rossi, and a large number of the older Taurus revolvers.

If you were to take the time to do some research on these revolvers, you’d see a striking resemblance to the old S&W. General Overview Occasionally, I run into problems with this design. Some of the problems I’ve encountered are: hard to close, hard to open, failure to open, and loose or sloppy lockup at the ejector-rod tip. The revolver used for this article is a Rossi Model 720 in stainless steel, but the corrective steps I’ll discuss can be adapted to any of the above revolvers.

The original complaint was a cylinder that was hard to open, a condition that could be caused by several problems. Let’s take a look at what they are. Of course, you’re going to make sure the revolver is unloaded, and all loaded ammo is out of reach. Start with some pre-disassembly troubleshooting and try to get a general idea of the problem and what might be causing it. Don’t get ahead of yourself and don’t overlook anything; the smallest detail missed could make a world of difference in the final analysis.

Continuing your detailed inspection throughout the disassembly process will save you time and aggravation. For disassembly instructions, I suggest you refer to The Gun Digest Book of Firearms Assembly/Disassembly, Part II: Revolvers, by J. B. Wood. Analysis and Correction A frequent problem that crops up in these revolvers, especially with the Magnums, is an ejector rod that has loosened under recoil.

If the rod backs out too far, it will compress the locking bolt in the underlug and bind up the cylinder to the extent that the cylinder will not open. The solution is to screw the rod back in and tighten it. Simple, you say, but it confounds many revolver owners (fortunately for us). Other reasons that can impair cylinder lockup or unlocking include a hand that’s too long, a bent ejector rod, a sticky ejector bolt, no bevel on the ejector rod, a bent yoke, or a center pin that’s too short.

All these problems can be found simply through a meticulously detailed inspection. The bolt should be flush with the recoilshield face. As I mentioned, the Rossi that inspired me to write this article had a cylinder that was hard to open. It had me befuddled until I decided it was time to get back to basics. (I should have taken my own advice about not overlooking any small detail.) The Rossi checked out fine, except for one area’its cylinder-locking system which locks at both ends.

In the photo at the bottom of this page you can see where the center pin makes contact with the center-pin bolt in the frame. The bolt face should be flush with the recoil-shield face. If the bolt was too short, it would cause a problem and it would either have to be built up or replaced and refit. You can see that the center pin has left a mark on the bolt face which continues on across the shield. It looks ugly but hasn’t hurt anything yet.

I found that the center pin tip had a sharp point on it that wasn’t polished off at the factory. It was a simple matter to file off and polish. The sharp

tip left a burr at the edge of the centerpin opening which can be seen in the photo at the bottom of the page. A fine Dremel-tool stone took care of it, but this didn’t solve the unlocking problem. The next step was to remove the ejector-rod locking bolt in the underlug. This is where I got ahead of myself. The locking bolt looked good as did its spring, and the tunnel where the bolt and spring reside checked out fine with no abnormalities. With the locking bolt removed, the cylinder opened and closed smoothly.

But instead of going to the locking bolt in this sequence, I should have checked out the center-pin length first. They call this a rod check. With the cylinder fully assembled and the ejector rod tight, take a small-diameter object such as a dowel and push in on the center pin at the rear of the cylinder until it’s flush with the ratchet. Now check the opposite end at the ejector-rod tip. It should be flush; i.e., the center pin has to be the same length as the total assembly.

Mine was just a little shy of being flush. Also, the bevel at the ejector-rod tip was absent, with its inner edge sharp and ragged. If the center pin comes up short, a small amount can be filed off the rod tip, but first we must take one more measurement before taking that step. We have to make sure we have a good lockup with the locking bolt. (If the ejector rod is way too short, this might not happen, and it would have to be replaced and refit.) With the bolt in place, swing the cylinder up just short of lockup.

You should have about 1/ 8 inch or so of overlap. Just make sure you have enough overlap so you don’t come up short. Refering to the photograph above, I used a small fine-tooth file to trim the ejector rod to length, and Dremeltool stones to cut the bevel. A shallow bevel is sufficient, which is then polished. In the center of the photo is the locking bolt and spring.

In this case, nothing needed to be done to the locking bolt and spring, but if you’re working with a revolver that has seen a lot of use, replacement of these parts might be necessary to attain a good lockup. On the right is the ejector rod, trimmed to correct length. And in the center of the photo is the ejector-rod locking bolt. Conclusions/Recommendations The steps taken above solved the problem with this Rossi. The cylinder now opens and closes smoothly with good lockup at the front.

There has always been a lot of controversy over this type locking system’one argument being that it doesn’t really give any support to the front of the cylinder. If the locking bolt is worn out, if the hole in the rod tip becomes enlarged, or if the ejector collar is worn out, I would have to say the detractors have a point. Nevertheless, if the system is in good working order and the tolerances are held to spec, it does give good support. And it doesn’t take much to keep it in working order.

All the revolvers listed earlier have a lot in common, both externally and internally. Although the parts won’t interchange, they all function in basically the same manner. And while repair manuals for some of these revolvers are hard to obtain or nonexistent, there is a manual that can be very helpful when working on them. If you don’t already own a copy, you’d do well to purchase The S&W Revolver by Jerry Kuhnhausen for your revolver-repair library. I