Cartridge Conversions

As a young man, I worked on the guns I had to or needed to. Now that I am retired, I get to work on the guns and projects I want to. In my case today, that means old single shot black powder cartridge guns. I have changed the mix of guns several times as my interests changed and now my interest is with strange old beasts with exotic old names like Martini-Henry, Snider, Gras, and Rolling Block on the military side along with Model 95 Winchester, Model 8 Remington, and Polish-made Mauser rifles.

The handguns have followed the same path but it is the rifles that really interest me. The guns themselves are fun and interesting and my passion has become to buy old relics and refurbish them into shooters. I’m just enough of a romantic to like the idea that guns that were once inches from the scrap heap will still be bringing pleasure to some guy long after I am 41 Swiss from .348 Winchester; an easy conversion. The case is cut to length, fire formed, and ready to load. gone.

One aspect of the process that makes it so much fun is putting together ammunition to shoot in these old warhorses. Most are chambered in what today are considered oddball calibers. You simply won’t be able to walk down to your local superstore and pick up a couple of boxes of .577-450 Martini-Henry, .43 Mauser, .41 Swiss, or even .25 Remington, to mention just a few.

However, the availability has improved over the past several years and I have found brass for some of these old codgers available from companies like Graf & Sons and Buffalo Arms. While the increased availability is nice, the prices area bit extreme so I tend to still craft them myself. If you want to 348 Winchester; a more difficult conversion.

Because the rim is too thin, the twine on the case on the right is used as a spacer to fire form the case to headspace on the shoulder. shoot these old warriors and don’t have the tools or desire to make the cases yourself these area couple of places you may find brass for them.

If you’re a reloader, history buff, black powder shooter, or simply interested in the black powder cartridge rifles that were the transition pieces between muzzleloaders and modern smokeless repeaters and want to shoot your collection of "experienced" guns, you’re a candidate to join the wonderful world of cartridge conversions. Depending on the cartridge, converting an existing case to fit and function in a gun chambered in an obsolete caliber ranges from relatively easy to incredibility difficult.

The best source I have found for instructions on what cartridge to use and how to convert it to what you need is a book titled The Handloader’s Manual of Cartridge Conversions by John J. Donnelly. Of course, the Internet is an invaluable source of information. It’s also a

41 Swiss and 11mm Gras. Two very different rounds from the same .348 Winchester parent case. 300 Winchester Magnum to 11mm Mauser. The belt must be turned off the case, then the case cut to length and annealed well before fire forming. source of misinformation; the trick is to be able to tell them apart. Let’s take a couple of examples just to help you decide if this is something you might like to take on. Knowledge and restraint are the most important parts of gunsmithing.

Understanding the firearm and its design limitations is critical. If the gun was designed and built for black powder loads, please stick to black powder. Most of these guns are over 100 years old and many have been roughly treated and show the scars and wear. Don’t put your life and limbs in danger trying to prove how tough they are. Stick to moderate black powder loads! Nobody is looking after your safety but you.

An easy one, and the one that got me started in this silly pastime, is converting the .30-06 case to 8×57 Mauser. Yes, 8mm Mauser is available but when I was shooting my M1 Garand obtained from the DCM (Department of Civilian Marksmanship, the predecessor to the current Civilian Marksmanship Program) in competition I was accumulating a lot of empty military .30-06 cases 30-30 to .25 Remington.

This one really requires a lathe because the rim must be turned off, an extractor grove cut in, and then a run through a .25 Remington die before cutting to length. from DCM matches where they supplied the ammo. So, I had a couple thousand .30-06 cases available to me and knew all I needed to do to convert them to 8mm Mauser was cut them to length and run them through a 8x57mm die. Ta-da! Free 8mm Mauser cases! I figured free was good and I was hooked.

My next venture came when I acquired an Austrian M95 straight pull bolt rifle in 8x56mm R as adopted by Austria and Hungary in the 1930s. Back in the 1980s, ammo was pretty scarce for these. Although much more available today, it does represent another common step in converting cartridges. The round is made from the 7.62x54mm R Russian cartridge with the case rim is turned down to 0.554 diameter. This can be done on a lathe or with the case chucked in a drill press and a file.

The case is then cut to 2.25 overall length, annealed, and fire formed. In case those are new terms to you, annealing the case simply means heating the neck and shoulder area with a propane torch until it glows orange and quenching it in cold water. This softens the brass so it is less likely to crack on the next step.

The case is then loaded with a light charge of a fast-burning pistol powder, the case is topped with a filler (cornmeal, Cream of Wheat, or similar material) and either a card or a plug of wax is placed in the neck. Chamber in the rifle, point in a safe direction, and fire it. This will expand the case to fill the chamber, fire forming it into the wanted dimensions. The conversions we have discussed so far have been relatively easy but this foolishness can get pretty complex.

In reality, each cartridge is a puzzle unto itself and you will have to research each one. For a taste of what you have awaiting you, I’ll talk about two other examples. The first is the .41 Swiss round used in the Swiss Vetterli rifle. This was originally a rimfire cartridge but later in their history, the guns were converted to centerfire. There are a

43/11mm Mauser round can be made by converting the .300 Win Mag case. The belt is turned off, the case cut to length, and then fire formed. lot of the older rimfires that were never converted on the market. I was fortunate to find one that had been converted to centerfire and the ammunition was relatively simple to make. Converting to .41 Swiss starts with a .348 Winchester case, cutting it to length, annealing, and fire forming it. The example other is the French .43 Gras.

This is also made from .348 Winchester brass but here it is necessary to thicken the rim to 0.08. Making the rim thicker is a job for an experienced lathe operator who can turn what are basically washers of the proper thickness, both the inside and outside diameter, to fit the cartridge. However, there is an alternative method of making this case usable.

Rather than trying to machine a brass washer, I wound some twine around the case just forward of the rim until I found how much it would take to get a light crush fit when the round was chambered. When the case was fire formed, the shoulder was moved forward. With the twine removed, the case headspaced on the shoulder like a rimless cartridge rather on the rim. As long as you restrict yourself to black powder loads, this has proved to be a perfectly acceptable solution, at least for my gun.

One of the more complex conversions I have personally done was to convert .30-30 Winchester cases to .25 Remington for my Model 8 semi-automatic rifle. I took new .30-30 cases, chucked them in my little mini lathe, turned off the rim, and then cut an extractor groove in each case. Cases were then annealed, run through a .25 Remington die, trimmed to length, and loaded. They worked perfectly, cycled the action properly, and gave good accuracy with no misfeeds or jams.

I have since discovered that the brass is available from Graf & Sons so have not converted any more .30-30 cases. I instead use the time on converting brass for cartridges I cannot obtain or can’t afford. American Gunsmith Mailing List Policy Like many other publishers, we make portions of our customer list available to carefully screened companies that offer products and services we believe you may enjoy.

If you do not wish to receive these offers, and/or information, please let us know by contacting us at: American Gunsmith Opt-Out Program Norwalk, CT 06854 Please include your current mailing label. A final word of caution. I have touched on just a few conversions of the hundreds that can be done for obsolete ammunition in both rifle and handgun calibers. Please, thoroughly inspect the firearm or have it looked over by someone that can verify that it is safe to fire. Research any project you take on.

Slug the bore of your gun and be sure to use a bullet of appropriate diameter and weight. Keep powder charges on the light side until you are confident it is safe to increase the charge. Better yet, confine yourself to light loads and enjoy the firearm for its historical value. If you want and need a magnum load there are plenty of modern rifles in currently-available calibers that are better suited to that task. Always err on the side of safety and caution.

We are all doing this for pleasure, so be safe and have fun. AG