The Hobby Gunsmith

May Feature-

1851 Navy Conversion

Readers of the Hobby Gunsmith have probably already concluded that we like cartridge conversions. In fact, Walt Kirst of Kirst Industries has been a supporter of the Hobby Gunsmith since the beginning. It was my intention to do another conversion project in order to convert some of my existing percussion revolvers over to cartridge. The reason I've chosen to do this is that the Single Action Shooting Society made a decision to change the loading rules for percussion revolver shooters and feel the new rules are unsafe. For this reason I've chosen not to stop shooting percussion revolvers in cowboy action competition.

   We were wondering what project to start next when the phone rang and it was none other than Walt Kirst himself. Walt offered me one of his new 38 caliber cartridge conversions for the 1851 Colt Navy. What made this particular conversion special is that it has his new backing ring with a functional loading gate. It took about two seconds to accept Walt's offer to convert one of my 51 navies over to 38 Long Colt. One condition of the offer was that he wanted me to only use readily available tools for illustrating this conversion. That meant no milling machine and everything had to be done by hand using either a file or a hobby grinding tool that might be readily available to the average hobby gunsmith.

   Another thing Walt asked was if we would be willing to provide him with a copy of the article in a somewhat edited format, and to allow him to use these instructions in his conversion kits. We certainly agreed to these conditions and he sent the new 38 Long Colt ported conversion cylinder along with the new spring-loaded loading gate.

51 Navy revolver prior to conversion with the new cylinder just below the barrel.

   Some people wonder why a person would spend the money to convert to a 51 Navy revolver into the cartridge firearm win a Ruger or another clone can be bought for only a couple hundred dollars more than the 51 Navy and conversion kit. We can think the two reasons why a person would convert a black powder firearm: they already have a .36 caliber Navy revolver or they want to be able to shoot in traditional and frontiersman categories. The conversion kit does allow a person to switch back and forth between percussion and cartridge shooting. This makes one gun become fully functional almost all in cowboy action shooting categories. Only percussion conversion revolvers can shoot in so many categories, because standard revolvers cannot shoot in the percussion categories.

   We started the conversion process by taking apart the 51 Navy percussion revolver. To disassemble this revolver, we start with a small brass punch on the right side of the frame and drift the wedge out the left side with a small hammer. The wedge on my Pietta Navy revolver must be completely removed to remove the barrel. This is done by depressing the retaining spring and pulling the wedge out the left side of the frame. The gun can then be put into the half cock position and the loading lever can be used as a ram to remove the barrel assembly when the ram is operated and forced against the cylinder.

   After removing the barrel from the frame, and with the gun still in the half cock position, the percussion cylinder is removed from the frame by pulling it forward and off the arbor. The arbor is the large axel the cylinder revolves around. At this point, We removed the Kirst backing plate from the box and put it into place with the firing pin area locked into the hammer recess. Be sure the loading gate is open before attempting to seat the backing plate into place. If the gate is not open, the backing plate will not move into place as the loading gate will bind against the standing breech. The loading Port will not close until after metal has been cut away from standing breach to form the new loading port.

Percussion revolver with new cylinder mounted in the frame to test the fit.  The loading gate will not close until the loading port has been finished.

   With the baking plate in place we loaded 5 pieces of .38 caliber casings into the new cylinder and slid the cylinder into place on the harbor. After assuring that everything fit properly, we reinstalled the barrel assembly. With the hammer still pulled in the half-cock position we used a feeler gauge to check the barrel to cylinder gap to make sure things were within acceptable parameters. The headspace measured to be .004 inches, which we believe is acceptable for a black powder firearm. The original headspace on this particular gun and had been .002 inches and we had not experienced any fouling problems.

   This particular 51 Navy revolver had been used as part of a two gun set for shooting in the gunfighter category of SASS. I had always used this gun with either Hodgdon's 777 powder, or more recently with American Pioneer Powder. It was my experience that a 20 gr. load of American pioneer powder was about perfect for this particular gun. This will be very close to the .38 caliber load we will be using in the cartridges.

   One consideration for the hobby gunsmith is that the .38 caliber bullet is actually .357 inches in diameter, whereas the 51 Navy revolver is a .36 caliber firearm. One might think the .36 caliber barrel would be a smaller diameter bore, but the opposite is the case. The 51 Navy revolver has a barrel bore that is .375 inches in diameter. When firing the .38 Long Colt bullets through the 51 Navy revolver, it is necessary to use a hollow base bullet to maintain accuracy.

   We purchased a 38 caliber Rapine bullet mold from Buffalo Arms. This mold looks like a normal round nose flat point bullet but has an insert that creates a deep hollow base. Under normal shooting conditions the pressure behind the bullet should force an expansion of the bullet skirt against the rifling lands of larger 51 Navy barrel. The should maintain accuracy when shooting this gun with the cartridge conversion. It did taking some searching to locate a supplier of the Rapine mold, but ordering online allow me to have the mold delivered within a week.

    After determining that the new parts are going to be a perfect fit and matched our gun, we disassembled the revolver by loosening the screw at the butt of the grip. We then removed the two screws from the top strap into the frame and then the screw to remove the grip and the top strap.

We then removed the mainspring screw and mainspring. We then removed the three screws surrounding the trigger guard and removed the trigger guard and grip frame. We then removed the 3 retaining screws on left side of the frame that hold the cylinder bolt, the trigger, and the hammer. All parts will now slide out through the bottom. This completes the disassembly of the firearm.

The machinists dye has been marked to match the backing plate and we are ready to start removing material.

   Although Walt Kirst provides a template that can be cut from the instruction sheet and placed against the standing breech, we always use the backing plate and as my template. We used machinists dye and coated the inside surface of the standing breech where the backing plate fits. After the dye dried, we put the backing plate into place with the loading Port open and used a scribe to draw the area of the standing breech and recoil shield that needs to be cut away to accommodate loading and unloading of the revolver. This process is illustrated in the photos.

   With the loading Port marked in the blue machinists dye, we clamped the frame to the bench and started filing. Although the frame of the revolver is color case heartened, We did not detect any resistance to the file while attempting to remove metal during the first stages of cutting the loading Port.

   One tip we recommend is to use a hobby grinder with a small standing drum to cut through any case heartening that might be present and to provide a notch that will help keep the file in place prevent it from jumping out and damaging the finish of the frame. It can be difficult to start filing on a rounded surface while keeping the file under control. Another precaution we take is to use duct tape to protect the surrounding surfaces to prevent damage in the event the file should slip. We placed duct tape on each side of the loading port as a guide to show how much to cut. The tape also provides some protection if the file slips or the hobby grinder should get away.

   We began filing with a round rattail file to cut the loading Port into the recoil shield. Work slowly and carefully and it'll take a couple of hours of filing to achieve the desired result. Progress can be speeded up by using a carbide bit in a hobby grinder to cut metal more rapidly. Be very careful to maintain control of any power tool while cutting on the side of the frame, because any slip may propel the tool right across the beautiful color case hardened finish of the revolver.

The early cutting of steel was done with a rattail file after making a cut through the case hardening with a sanding drum.

   An alternative to using a carbide cutter would be to use a small sanding drum in a high-speed grinder to slowly cut metal away from the area where cartridges will be loaded. We used a quarter inch dye grinder with a quarter inch carbide bit to open up the area quickly. We caution people when using powerful tools to be careful not to overheat the frame and change the characteristics of the underlying steel. It is safe as long as you can still touch the frame without burning your hand. Be aware of how hot that frame is becoming and carefully grind. Another caution we offer for anyone using a carbide cutting tool is that these cutters tend to produce small but very sharp slivers that will stick into the skin. We recommended a shop vacuum be set up near where the chips are flying off so they are vacuumed right out of the air. We also strongly recommend using a face shield and safety glasses while using any power tools. Follow the directions that come with your tools.

The cut is regularly tested to prevent cutting too much and to know when a cartridge casing will easily pass through the loading port.

   Patience is very important when cutting steel to form the loading port regardless of whether you're using hand or power tools. One should often check to see how close you've come to the lines scribed into the dye on the standing breech. As we approach the point where we might be able to load cartridges, we stop, remove the duct tape, clean off the chips, and assemble the backing plate and cylinder to see how close we are to being able to remove and insert an empty .38 cartridge.

   And as we get closer and to the lines drawn in the machinists dye, we transition from the carbide cutter to a small sanding drum. We start with a course grit and focus on rounding the bottom of the loading port. As the port approaches its final size, we transition to a finer grit and begin truing the bottom of the loading port. We eventually found it was necessary to fit a the backing plate and the cylinder, along with empty cartridge casing to test the clearance of the ammunition being fed into the chamber. It required several more sessions of working with the sanding drum to get the correct size, which also required fitting the backing plate and cylinder each time.

   After it was determined the loading port was the correct size and shape, it was necessary to install the backing plate and cylinder one last time to check the fit and function of the loading gate. The first attempt results in the loading gate not closing correctly because it was still closing against the loading port wall.

   We installed a small fine-grit sanding drum in the small rotary grinder and began working carefully to match the loading port precisely to the backing plate. This was done with the plate in place and after we had a good match, the loading gate closed properly and the process of fitting was complete.

   The next step was to use the rotary sanding drum in a pin vice. Using the pan vice as a handle, we wrapped 400 grit wet or drive sandpaper around the rubber sanding drum. We applied a small amount of unscented mineral spirits to the 400 grit wet or dry sandpaper and began sanding parallel to the loading port to polish out the grinding marks. This required about 10 minutes of work and resulted in a very smooth loading port.

The finished loading port is now sanded and ready to be buffed prior to being cold blued.

   We then used the small rotary grinder with a small bullet shape buffing wheel loaded with emery buffing compound to buff out any final standing marks, which gave us a highly polished surface in the loading port that was ready to be cold blued for rust protection. The parts were cleaned to with gun scrubber to remove any remaining oil or grease from the grinding and buffing process.

The loading port has been buffed using emery and is now ready for cold bluing.

   We used to a cold bluing process from Caswell plating that has been featured in previous articles of The Hobby Gunsmith. We used a Q-tip to dab the cold bluing solution onto the freshly polished loading port. After letting the solution set and oxidize the steel for a few minutes, we carded it off and buffed it with 0000 steel wool. It required several applications of cold bluing solution to get a nice brightly polished and blued surface in the loading port. We used a little Birchwood-Casey cold bluing solution in spots to slightly simulate the color of the color case heartening of the rest of the frame.

The finished frame ready for final assembly and oiling of the gun. 

   With the loading port of the frame properly blued, we used unscented mineral spirits to clean the frame and all other parts that had come out of the gun. The gun was reassembled with all parts properly oiled and applied grease on the arbor where the cylinder fits. Final assembly was to install the barrel and all parts like any other gun that's been cleaned. The amazing part of this conversion is that it only took about three hours from the time we began the process of taking the gun apart until it was reassembled and the final photos taken.

The original Navy on the left and the converted one is on the right.

We admit to using a more powerful quarter-inch dye grinder instead of a hobby grinder, but that probably only saved about half an hour of work. Any hobbyist could complete this project on the kitchen table in less than four hours with just a rattail file, a hobby in grinder, a little sandpaper, and some cold bluing solution. This is an excellent project for the beginning hobby gunsmith who is limited in the available tools.

The two 51 Navy revolvers.  The top one has been converted while the lower one remains true to the original.

   Ever since I started shooting cowboy action I have wanted to own a 51 Navy conversion. For the last four years my desktop computers desktop has been a downloaded photograph of a pair of 51 Navy revolvers with one converted to cartridge, but they've always alluded me in actually owning one. I am now the proud owner of a 51 Navy conversion that looks as good as any of the factory conversions.

A close-up photo of the Kirst Konverter fully installed and ready for a trip to the range.

   Walt Kirst has certainly outdone himself with this new backing plate with a fully functional loading gate. The Kirst Konverter and a hobby grinder quickly allows the owner to convert an inexpensive 51 Navy revolver into an authentic appearing conversion. The only component still missing from the conversion is an extractor housing, which will be the subject of a future article as soon as we figure out how to make a natural appearing extractor housing. This 51 Navy revolver was one of a pair and we assure you that the other matching revolver will be similarly converted in the near future.

Update: 51 Colt Gated Konverters are not yet available.  Due to construction and equipment problems at the machine shop it is not possible to give a definitive answer as to when full production will start. All we can say is: Kirst parts will be running as soon as the new machining center is operational.  

Makers of fine Cartridge Conversion kits for:

  • Remington New Army

  • 1851 and 1861 Colt

  • Ruger Old Army