Tightening A DA Revolver's Cylinder
January 03, 2011
How many times have you picked up a used revolver and noticed side-to-side movement of the cylinder when it was locked in the frame? If you're like me and are always looking for a bargain, you've probably run across quite a few well-worn revolvers like this. It's a mystery to me why more well-worn revolvers aren't repaired. More often than not many of these revolvers can be "tightened up" with just a limited amount of work and a few new parts. While you may not ever do it yourself, you might find it interesting to see just a part of what's involved and how a gunsmith would handle it. It's not as big a deal as you might think.
The sample S&W Model 18 DA revolver displayed noticeable side-to-side movement of its cylinder. This movement can be caused by wear on the cylinder stop tab (T), wear on the cylinder stop slots (R), and wear on frame slot (L). The condition can be fixed by installing an oversize cylinder stop.
I had a nice old .22-caliber Smith & Wesson Model 18 in my shop that had seen a lot of use. Based on what I was told, I wouldn't be surprised if this revolver had fired between 50,000 and 75,000 rounds. By normal standards, that's a lot of shooting! Even with such extensive use, the revolver was in nice shape. The blueing was a bit worn, but there was no rusting or any indications that it was ever abused or neglected. In fact, the only sign of wear was the looseness of the cylinder.
Ideally, there should be little or no perceptible side-to-side movement of the cylinder. If there is movement, it's quite possible that the chamber will not be aligned with the bore when the gun is fired. If it's misaligned, the bullet will slam into one side or the other of the forcing cone at the rear of the barrel. If it's bad enough, the bullet will even miss the forcing cone! This can result in lead being shaved from the bullet, which can be dangerous to the shooter or bystanders. This old Model 18 had quite a bit of side-to-side play, but there was no indication that it was "spitting" or shaving lead. Also, there was no fore and aft movement of the cylinder.
The side-to-side movement could be caused by a number of factors. The cylinder stop, a precisely fitted part designed to hold the cylinder in place when the gun is fired, could be worn. The portion of the cylinder stop most likely to wear is a tab or small bar-like projection that extends through the frame and engages milled slots in the side of the cylinder. Ideally the width of the cylinder stop tab will match the width of the cylinder slots. If the cylinder slots have been enlarged or if the cylinder stop tab is worn and slightly thinner than needed, the cylinder will not be locked securely. There will be enough "slop" for side-to-side movement.
Another possible cause of this cylinder movement relates to the fit of the cylinder stop in the frame. As I mentioned the cylinder stop tab projects through a slot in the frame in order to contact the cylinder. This frame slot can also wear and permit side-to-side movement of the cylinder stop tab. This in turn allows movement of the cylinder.
Simple replacement with a new standard factory cylinder stop will not necessarily correct the problem. If there is wear on the cylinder slots and/or in the cylinder stop slot in the frame, a new cylinder stop may not be large enough to compensate for all this wear.
What is needed is an oversize cylinder stop. Fortunately, such an item is readily available. For this old Model 18, I used one of the Power Custom oversize cylinder stops; it can be purchased directly for about $30.
Reid's revolver exhibited side-to-side movement of the hammer and the trigger. He fixed those areas by installing hammer and trigger pivot pin shims.
Step 1: Disassemble The Revolver
The first step in the rehabilitation of the revolver was to remove the cylinder. Obviously, before you begin any gun repairs, always make certain the firearm is unloaded! Following the removal of the cylinder, I took off the sideplate and removed the mainspring, hammer, and rebound slide. As I removed those parts I noticed wear marks and scratches on the sides of the hammer and the trigger. That's not good! Those marks are indications that the hammer and trigger are dragging on the inside of the frame as they are cycled. This makes for friction and a heavier trigger pull. It can also decrease the energy with which the hammer strikes the firing pin. In short, this is something we want to avoid.
The drag marks were made by burrs on the inside of the frame, and I removed the burrs with a bit of judicious stoning. I used a medium India stone and was extremely careful to avoid contact with the bosses, or raised shelves, around the hammer and trigger pivot pins. Never remove these bosses as they help to prevent contact between the sides of the trigger and hammer and the inside of the frame. Once the burrs were removed, I carefully and thoroughly hosed out the inside of the frame with Tipton Insta-Clean available from MidwayUSA. You absolutely must remove any and all traces of grit left by the stone. If you don't, it will cause trouble.
I installed the hammer and then the trigger to check movement back and forth and side to side. I found that even with the burrs removed I still had a problem. The hammer and trigger would shift from side to side on the pivot pins.
Fortunately, Power Custom also has a solution to this problem! The solution is tiny stainless-steel washers that are only .002 inch thick (that's two-thousandths of an inch). These washers are placed over the pivot pins on either side of the hammer and trigger until there is no side-to-side movement. You have to be careful that you don't use so many that they compress on the trigger and hammer when the sideplate is installed.
Step 2: Check The Cylinder Stop
With the trigger and hammer taken care of, I returned to the problem of the cylinder. I checked the fit of the cylinder stop in each of the stop notches in the cylinder. The Power Custom oversize cylinder stop was a nice snug fit with no side-to-side slop. I also checked the fit of the new cylinder stop in the frame slot. Again, there was much less side-to-side movement than with the old cylinder stop.
Before installing the cylinder stop I used an India stone to carefully break the sharp edges of the locking tab. This would help to prevent any possibility of the top of the tab scratching the surface of the cylinder. Just one or two strokes with the stone was all that was necessary. Some folks go so far as to polish the top of the tab, but this new part was incredibly smooth right out of the package.
An important aspect of a DA revolver's mechanism is the relation between the trigger and the cylinder stop. 1) Trigger At Rest In Forward Position 2) Trigger Pivots Down, Pulls Cylinder Stop Down, And Disengages Cylinder Stop Tab From Cylinder 3) Trigger Disengages From Cylinder Stop, And Cylinder Stop Is Pushed Back Up 4) Trigger Continues To Move Back, Cylinder Rotates, And Cylinder Slot Aligns With Cylinder Stop Tab
Step 3: Reassemble The Revolver
The revolver was reassembled with the new stainless-steel washers and the new oversize cylinder stop. I left the sideplate off so I could check the fit and function of the new cylinder stop. The revolver was carefully cycled, and the function and movement of the cylinder stop were observed.
The timing of the cylinder stop is critical, and this is controlled by the forward portion of the trigger. As the trigger is squeezed, a projection on the front of the trigger engages a shelf on the rear of the cylinder stop and pulls the tab of the cylinder stop down and out of the locking notch in the cylinder. The cylinder is then allowed to begin to rotate. As the trigger continues to move it disengages from the cylinder stop. At this point a spring pushes the tab of the cylinder stop up against the cylinder so it can drop once again into the next locking notch.
Very little fitting was required, which is a tribute to the outstanding product from Power Custom! The cylinder now locks up with virtually no side-to-side movement.
With just a simple oversize cylinder stop and a few stainless-steel shims, this nice old Model 18 was ready for more shooting.
In fact, I'd go so far as to say that it is probably better now than it was when it was brand new and right out of the box. So the next time you run across a well-used old Smith & Wesson double-action revolver, keep in mind there might be a lot of life left in that old girl!
By the way, for detailed instructions on the fitting of the cylinder stop I strongly recommend The Smith and Wesson Revolver, A Shop Manual by Jerry Kuhnhausen. It's an outstanding book and available from most gunsmith supply houses.
Until next time, good luck and good gunsmithing!