Troubleshooting the Cimarron Model 1872 Open-Top Revolver

The revolver that is now commonly known as the "Open- Top" was Colt’s first mass-produced revolver that was specifically designed to accept metallic cartridges. This model came along in 1872, and is highly prized by collectors because it was the immediate forerunner of the famous Single Action Army.

Even though Open-Tops look very much like earlier percussion revolvers with the barrel fastened by a wedge, they were not converted capand-ball revolvers; they used a frame that was specifically intended for metallic cartridges. The Open- Top frame was machined to ac Above and This gun is chambered in readily available .44 Special caliber. Although it appears very similar to a Colt percussion or cartridgeconversion revolver, the Open-Top was the first real metallic cartridge revolver to be produced by Colt.

The close-up view of the Cimarron Open-Top shows the great attention to detail given by the Italian gun manufacturer, Aldo Uberti. cept a loading gate that pivoted on a screw, and it did not use a separate conversion plate like the one previous converted Colts had. Still, it appeared to be a throwback with its open-top-type frame, along with the barrel held with a wedge like Colt’s percussion pistols.

The Richards and Richards-Mason conversion revolvers made by Colt during this same time were chambered to fire the .44 Colt centerfire, but all of the 7,000 Colt Open-Tops were chambered for the .44 Rimfire cartridge. William Mason’s newly patented rod-ejector was also used with Open-Tops, and it fastened through the barrel’s underlug exactly as it did with the Richards-Mason conversion revolvers. This rare and unusual .44 Rimfire revolver is not likely to turn up in repair shops these days.

Neverthe less, the modern replica made by Uberti and marketed by Cimarron Firearms will be showing up. In fact, Cimarron’s Open- Top is becoming a familiar sight at cowboy-action matches. Most

Far collectors and shooters will quickly agree, Colt’s Open-Top was a real classic revolver with exceptionally beautiful lines, and if a gun can have such a thing, the Open-Top has "sex appeal." Aldo Uberti’s company has kept the original graceful lines of the replica very much the same as the original.

The real benefit for today’s shooters comes from the fact that the modern-made version is available in off-the-shelf calibers such as .38 Colt and .38 Special, .44 Colt BHA, .44 Russian, .44 Special, and .45 S&W Schofield. Both the original and the reproduction Open-Top revolvers were available with either the Navy size (Single Action Army size) grip, or the longer 1860 Army grip. Cimarron Firearm’s new O-Tis available with either 5-1/2- or 7-1/2-inch barrel lengths and in several choices of finishes.

On a personal note, I have been having a great time shooting my .44 Special caliber Open-Top (pictured); this thing is a real pleasure to shoot. Moreover, the gun is wonderfully accurate. Using Winchester’s Cowboy Action loads, the revolver gives me five-shot groups as small as 3/4 inch at 25 feet—that is, if I do my part.

Just like the Colt, Cimarron’s 1872 has a rear sight that’s integral with the barrel, so even though the sight radius is relatively short, a much steadier sight picture is possible than with percussion Colts, whose rear sight was a notch in a wobbly hammer. Uberti has added an unusual safety device to the hammer that can only be seen or operated when the hammer is pulled to the rear. This is mounted about two-thirds of the way up on the hammer face.

Just under the firing pin is a small screw which when turned, rotates a solid-steel block forward. When the safety bar is in this position, it prevents the hammer from falling all the way down. Mechanically, the safety is quite effective, but on the practical side it is very slow to use and too cumbersome to be used effectively for anything except to provide an excellent safety method during storage. One other feature of Open-Tops, both old and new, are the cylinder gas rings.

On this revolver, the gas ring performs two important tasks: One, it keeps the cylinder pushed to the rear so constant headspace is maintained; and two, the gas ring helps to keep high-pressure blackpowder gases from entering the base-pin area, where they would eventually foul the cylinder and interfere with its rotation.

Percussion Colts and conversion Colt revolvers did not have this excellent feature (actually an 1870 S&W innovation.) The fact that the Open-Top cylinder does have a gas ring will allow shooters to fire blackpowder loads successfully, without the annoyance of the cylinder binding because of powder fouling. Takedown Instructions These instructions will work with original Colt Open-Top and modern Uberti-made replicas thereof that are based on the traditional Colt design.

For purposes of clarity, I use the Uberti parts nomenclature in these instructions. 1) Before we begin, let us be certain the weapon is unloaded. Always point and hold the muzzle in a safe direction, a direction that would be facing away from any person, pet, vehicle, or dwelling. Remember, bullets can go through plaster walls. Keep your fingers away from the trigger during this entire operation.

Check to make absolutely sure this weapon is unloaded by opening the gate (#142), now pull the hammer (#2) slowly to the rear until you have heard one audible

The front screw (#144) is what holds the ejector rod tube onto the barrel. The rear screw (#33) is the wedge screw. click. This places the hammer in the half-cock or what is called the "loading position" and the cylinder (#5) should now spin freely in a clockwise direction.

Slowly rotate the cylinder two full revolutions by hand, all the while examining the cylinder’s chambers through the opening presented by the opened gate at the rear of the frame (#1) to make absolutely certain that the cylinder chambers have no cartridges in them. What should you do if the cylinder has cartridges in it? Be aware that this is a loaded gun! Proceed by pointing and holding the muzzle in a safe direction as discussed above.

Leave the hammer exactly where it is—in the half-cock or loading position and with the gate still open. Use your left hand to hold the revolver securely by its grip, and still keeping your fingers away from that trigger, tilt the revolver so the muzzle is facing away from you and upwards. Next, use your right hand to rotate that cylinder slowly, one chamber at a time.

You should For normal cleaning purposes, this is as far as you will need to disassemble the revolver. pause at each click and allow each successive cartridge to fall out of its chamber and onto the workbench. If a cartridge will not fall out by its own weight, you should manually operate the ejector by pushing the ejector rod head—Uberti calls this the ejector rod nut (#164)—which is located under the front of the barrel.

Push it to the rear with your right hand, and the ejector rod will force that cartridge out of the chamber. When you are sure that there are no more cartridges left in the cylinder chambers, you can continue with the disassembly procedure below. 2) To remove the barrel and cylinder, the hammer should still be resting in the loading or half-cocked position and the gate should still be open. Unscrew and remove the ejector-rod tube screw (#144) from the left side of the barrel (#3). This is the front screw of the two.

The ejector-rod assembly (#143) is now loose and can be removed from the right side of the barrel. Loosen the wedge screw (#33), the rear one of the two screws on the left side of the barrel, until the flat portion of the screw head is facing down. Drive out the wedge (#4) from right to left using a soft drift punch and hammer, and remove the wedge from the barrel, make note of its position for reassembly. The barrel can be pulled straight forward and off the frame.

If the barrel is stuck in place, try driving a small, tapered hardwood wedge between the lower front face of the cylinder and the barrel until the barrel breaks free. The cylinder (#5) can now be removed by pulling it straight forward and off the base pin (#21).

Cimarron Firearms Model 1872 Open-Top Revolver 1 Frame 2 Hammer Assembly 3 Barrel 4 Wedge 5 Cylinder .38 Special 7 Hand Assembly 8 Backstrap 10 Trigger 11 Grip 12 Bolt 15 Sight 18 Hand Spring 3) The grip and grip strap are removed by unscrewing and removing the two back-strap screws (#32) from the top-rear of the back-strap (#8). Then remove the single butt screw, called the connect screw (#455), that faces up from the butt of the back-strap.

The back-strap and the one-piece grip (#11) are removed by pulling them down and to the rear as a unit. Once these parts are off the frame, the grip itself can be pulled straight forward off the back-strap. Unscrew 19 Trigger Bolt Spring 20 Main Spring 21 Base Pin 23 Barrel Pin 25 Roller 26 Triggerguard 30 Hammer Pin 31 Front Triggerguard Screw 32 Backstrap and Trigger Screw 33 Wedge Screw 35 Trigger Bolt Spring Screw and remove the mainspring screw (#36) from the inside-lower area of triggerguard (#26).

The mainspring (#20) is loose.

Unscrew and remove the two triggerguard screws (#32) and the front triggerguard screw (faces up, #31) and the triggerguard (#26) will fall straight off from the bottom of the frame. 4) To disassemble the action, first remove the trigger and bolt-spring screw (#35)—the only screw inside 143 Ejector Rod Tube 144 Ejector Rod Tube Screw 145 Gate Catch Screw 147 Hammer Safety Spring 149 Safety Spring 152 Hammer Safety Stop Screw 164 Ejector Rod and Head 455 Connect Screw 675 Gate Screw 36 Main Spring Screw 37 Hammer Screw 38 Trigger Screw 40 Bolt Screw 91 Hammer Safety Bar 98 Firing Pin 135 Ejector Spring 136 Gate Spring 142 Gate the frame that faces straight up—from the underside of the frame, and the trigger and bolt spring (#19) will fall out the bottom of the frame.

Unscrew and remove the forward-most of the three screws on the left side of the frame. This is called the bolt screw (#40), and it holds the bolt (#12) in place. With the screw out, the bolt can be removed from the bottom. Try to keep the bolt screw with the bolt while they are removed; this is because the trigger screw (#38) can

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easily be mistaken for the bolt screw (#40), although the trigger screw is slightly shorter. Unscrew and remove the trigger screw and the trigger (#10) will drop out the bottom. The hammer screw (#37) can now be removed, after which the hammer assembly (#2) can be rotated slightly to the rear, then pulled down and out of the frame. The hand assembly (#7 and #18) is connected to the hammer and will come out with it.

Once the hammer assembly is out, the hand assembly can be removed from the hammer by simply lifting it up out of its socket hole on the left side of the hammer. Further disassembly of the hammer is not recommended. 5) If desired, the ejector tube can be disassembled like this: Push the ejector-rod nut (head) rearward to expose more of the ejector rod at the rear of the tube. Grasp the rod with padded pliers, and unscrew the rod in a counter-clockwise direction.

When the rod is free of the nut, pull it out through the rear of the tube. Compress the ejector spring (#135) with the tip of a small screwdriver and lift out the ejector rod nut through the front of the slot in the ejector rod tube. The ejector spring is now removed by pulling it out the front of the ejector rod tube.

The gate spring (#136) can be removed by unscrewing and removing the gate-catch screw (#145) and lift This provides a seal against powder fouling and keeps the headspace measurement intact. ing the spring away from the frame. The gate can be removed by first unscrewing and removing the gate screw (#675.) The base pin should not be removed.

If a problem exists with it, the revolver should be returned to the importer. (Note: when you reinstall the gate screw, I recommend touching the threaded hole in the frame with a tiny drop of Loc Tite blue thread-locker to help prevent the screw from backing out. Use care to keep the Loc Tite only in the internal threads and not on the gate pivot. As always, you reassemble the revolver in the reverse order. ■