Cartridge Conversion Percussion Revolvers- Info, Criteria and Process

It’s no secret by now that I am fascinated with Cartridge conversions of percussion revolvers. This all started with the local indoor ranges insisting on jacketed ammo only. It meant that my beloved .45 Colt’s were prohibitively expensive to shoot as I did not reload. Since times were hard I reluctantly parted with them. Then Linda surprised me at Christmas with a Cimarron Richards/Mason conversion- in .38 Special, which I could still afford to shoot!

CimmRM38

This was perfect on so many levels- I love the 1873, but that grew out of my love for the 1851 and 1860 revolvers. This was the best of all worlds- a gun type I loved in a caliber I could afford to shoot. It also represented a type that was more common in the old west than 1873s, and hearkened back to the Spaghetti Westerns of the early 1960’s.

With a bit of research I became aware of the cartridge conversion kits available from Howell, Kirst etc. I decided to do a cartridge conversion of my own, and circumstances (which I have detailed in earlier blogs) dictated that I do so on an 1858 Remington. I selected a Kirst .45 Colt conversion (.44 percussion revolvers are actually .45 caliber) because it was a simple drop-in and would be the easiest to install. It was, requiring only a tiny amount of fitting. Like Remington’s original factory cartridge conversions this is a five-shooter; there just isn’t quite room for the outside diameter of a .45 caliber cartridge to put six shots in the cylinder.

The Kirst Konverter is an excellent product, made of modern materials with proper heat-treat and a very high degree of finish. I was so happy with this product that when my next conversion project came along I bought another one, this time for a Colt reproduction. Again it worked a treat-aside from needing a drop of Loctite in the gate retention screw.

OT2ELra

But there is a problem with Kirst Konverters. OK, to be more accurate there is a problem with my finances; being self-employed and partially disabled my disposable income is pretty limited at times, which means a conversion project winds up sitting on the shelf for 3-6 months waiting for me to be able to afford the Kirst unit. So when another 1858 project showed up on my doorstep it was time for a different approach.

I had taken up reloading which opened the gates to more variety of cartridges, and these guns were originally chambered in .44 Colt or something very like it. These cartridges used a .44 caliber case loaded with a .451 bullet with a heel-base like a .22LR. This meant the casing had an outside diameter of .451-.454, and there is just enough room to bore out a .44 Colt or Remington cylinder to accommodate this cartridge. I had also procured a proper metal lathe, so I turned down the back of the cylinder and bored it through, then reamed the chambers to .454″.  I made a breech-plate from scrap 1/4″ 5160, which I have a lot of due to my day-job, mounted a floating firing-pin, cut a port for loading and voila! I had a home-spun cartridge conversion, very like the sort of things done by gunsmiths back in the day.

3moSUZK

Really the mechanics of the conversion were not difficult, and I knew it was possible because it was done safely in the 19th century even though the quality of the materials was lower. Getting the ammunition right actually proved to be a far tougher task and involved making special equipment to load the cartridges. But overall it was a success.

Since then I have converted an 1849 reproduction to .22 LR, an 1851/.44 to .38 S&W and a Walker to a .44-55.

ConversionFamiltPic

All of these conversion were basically done the same way- turn down the back of the cylinder, leaving the ratchet, then bore it through to accept cartridges. In the case of the .22 and .38 S&W I also lined the chambers and reamed them for the cartridge, and lined the barrel as well with rifled barrel-liner purchased from Numerich Arms. Then I made a breech-plate with a loading port and a floating firing-pin. In the case of the Walker conversion I mounted this to the gun’s blast-shield with screws. Each gun had it’s variations, but the basic process is the same.

So far I’ve done four home-spun conversions, and I plan to do more. But there is something you should understand- this is risky- even dangerous- if you aren’t me. I have been a knife and sword-maker for decades, and not only have the shop equipment I need, I have an encyclopedic knowledge of the strength and working properties of metals. I also have more than the common run of knowledge about firearms- though this is easy to remedy with sufficient research. You need to know though- there are no guarantees and it would be very easy to harm yourself or others if you get it wrong.

OK, in an excess of optimism or even based on genuine capability you have decided to go ahead and do your own conversion. I’d actually advise against it, but I will tell you how I made my decisions and what they were based on.

The first conversion I did myself was based on conversions that were done to original guns- I used a reproduction of a gun they used and made it for a cartridge from that application. The metallurgy of modern reproductions is a fair bit better than what was in use when these guns were new. We use steel where they used iron. Where they used steel makers today use better quality, more uniform steel. It is a safe bet that we can do anything to a reproduction that they did to an original.

Some background you should know- in the mid 19th Century all cartridges used black powder, and the cases were loaded by putting as much powder in as would fit,  then stuffing a bullet in on top of it. You literally cannot put enough powder in the case to blow up the gun without some external factor- like a plugged bore- contributing.  Similarly you cannot stuff enough black powder into the cylinder of a modern reproduction percussion revolver to blow it up. This makes 19th century cartridges an obvious choice to use in a cartridge-conversion revolver, even with smokeless powder.

ul1asfb

Here’s something else you need to know- it is perfectly safe to load smokeless powder loads in a cartridge designed for black powder loads. Back around the turn of the 20th Century when they converted to smokeless powder all common revolvers and derringers were designed for black powder cartridges. Yet the transition to smokeless powder was seamless. Why? Because ammo companies didn’t want to get sued and besides, blowing up people’s guns would make it difficult to sell their ammo. So they formulated loads that were safe to fire in cartridges designed for Black Powder.  Yet many people today are convinced this is unsafe. Why?

Because hand-loaders. They had a tendency to load the new smokeless powders as if they were black powder, and they blew up their guns. This was so common that catalogs of the period specifically noted that the new style of powder was loaded differently and used much less powder. The truth is that the laws of physics don’t magically change because one type of powder is more energy-dense and makes less smoke. Pressure is pressure, period. Burn rates, pressure curves etc. can all be compensated for. There are even people that load reproduction cap-and-ball revolvers with smokeless powder (though this often necessitates a better ignition system.) No, smokeless powders are not a high-explosives that can ‘shock’ the steel and cause ruptures if properly loaded.

The fail-safe method would be to use black powder cartridges loaded with honest-to-God black powder. This is safest for one simple reason- it is impossible to overload the cartridge. If you want to use smokeless do your research and stick to lower-powered loads. It’s also going to be prudent to pick a cartridge that was used in cartridge conversions, like .38 Colt or .44 Colt. This will require special equipment and heel-base bullets to reload, which is  bit of a pain in the butt if you aren’t seriously committed. Or just should be committed.  Regardless, this will provide your greatest margin of safety because you know it worked then and there is no reason it wouldn’t work now.

This gets harder when you are working with a cartridge that never existed- like .44-55 Walker, which I made up. The reasoning goes something like this- the wrought-iron cylinder of a Colt Walker could handle a 60-grain charge of black powder behind a 210 grain picket bullet. The steel that a modern reproduction is made of is mild steel equivalent to 1018-1020.  This is significantly stronger than wrought iron, so it will be safe to duplicate Walker loads in the modern reproduction.  Other people have bored-out Kirst .45 Colt cylinders to accept cartridges like .45-60-225- a .45 caliber, 225-gr. bullet over the equivalent of 60 gr. of black powder. The Kirst cylinder is of course much tougher than the reproduction cylinder, being 4140 tool steel that has been heat-treated to a half-hard state- but the load is still only a little over the limit for the original iron cylinder. Still, the repro cylinder is less strong than the Kirst, so it is better to err on the side of caution and not quite equal the original Walker load.

I also decided to make my cartridges out of rifle brass- .303 British, actually- because this brass is much stronger than should be needed. Once expanded to take the .45 caliber heel-base bullet and fire-formed the cartridge will accommodate a 55gr. charge of FFFg. Thus the name- .44-55 Walker.  Since my winter shooting is pretty much restricted to indoor ranges I wanted a smokeless load, and I selected Trail Boss for this because it is a relatively safe alternative to black powder, and unlike some other powders it will not leave a large void in the loaded cartridge, which can cause poor ignition or, in a worst-case, detonation. Using the manufacturer’s recommended process for developing loads the case will hold 13.4gr of Trail Boss, so I backed it off to 10gr. as a starting point and this has worked out just fine. A friend’s wildcat, .45 Walker, uses a 225 grain bullet over 12 grains of Trail Boss, so I reckoned 10 made for a pretty safe load, and so it has proven in use.

So I started from a reasonable assumption, checked with other people’s experience and proceeded methodically, erring on the side of caution. Similarly deciding to chamber the brass .44 in .38 S&W. The recommended load is a 173gr. .451 ball over 15 grains of black powder. This is about half the maximum charge for the cylinder, so I know the cylinder can easily take it. 173gr projectile over 15gr. of Black powder won’t over-stress or stretch the brass frame. My .38 S&W was normally loaded with a 147gr. bullet over 11-12gr of black powder, so the modern equivalent is well below the threshold of the recommended load for the gun. Since I actually added metal by lining the chambers and bore the gun is even stronger than stock, so it is reasonable to assume it will be fine with the .38 S&W loads.

But- while I can be virtually certain the gun won’t grenade on me the smaller diameter cartridge will generate higher pressures than the same load in a larger cartridge, and it might stretch the frame more than expected. I don’t really expect so; equal and opposite reactions and all that; between the ball, fiber wad and powder charge of the recommended .44 load it’s throwing a lot more weight downrange, so it’s going to have significantly more recoil. The good news is the worst frame-stretch will cause is inconsistent ignition as the primers get too far away from the breech, and excessive cylinder-gap blast. In other words a failure will not only be obvious, but it will render the gun inoperable before it is catastrophically severe.

A lot of thought goes into my conversions- and the thought I cannot escape is that it would be better to leave it to professionals. Products like Kirst and Howell converters are made from better materials and processes than I can employ by people with a lot of experience.  They can also steer you to professional gunsmiths like Gary Lee Barnes that do conversions using their products and produce exceptional results. The fact that some schmuck can do this in his home workshop and hasn’t blown himself up yet does not make it a good idea.

Yes, I am going to continue, against my own advice, to make cartridge conversions. But I am going to do it carefully, thoughtfully and cautiously, and never forget that what I am doing is inherently dangerous.

Michael Tinker Pearce. 29 April 2018

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s