We’re all gun enthusiasts here, but most of us aren’t into every conceivable sort of gun, hunting or shooting sport. You can be forgiven if you don’t understand or have misconceptions; I am not trying to talk down to anyone here, just educate.
First let’s talk about gunpowder. If there isn’t enough for the volume behind the bullet dangerous conditions can occur. Normally gunpowder ignites from the rear and combustion progresses from back to front, allowing pressure to build gradually and fairly uniformly. Whether it’s black powder or smokeless it’s pretty much the same.Â But if there is too much room behind the bullet you can get flashover. This is when the fire of ignition passes over the powder and ignites a much greater percentage of the powder much more quickly, causing pressure to spike almost instantly and sometimes reach unsafe levels. This is called ‘detonation’ and it can cause the cylinder to fail. Steel is tough, but it has elastic limits, which includes how fast it can expand or resist pressure. How bad this is likely to be depends on how fast-burning the powder is; Black powder burns super-fast (if inefficiently) but in smokeless powders it’s the slow-burners that will get you.
This is more of a danger with Black Powder because black powder is classified as an explosive. This means it ignites very easily and burns very, very fast. This is why you always use a compressed load of black powder; either by using enough powder that you need to compress it by seating the bullet or by using a filler to insure that the powder is under compression. While it is rare with modern metallic cartridges and smokeless powder it can still happen, particularly with small loads of slow-burning powders in (relatively) large cases.
This leads to another issue; many people feel it is unsafe to use smokeless powder in cartridges designed for black powder firearms. It is and it isn’t, so let’s talk about that. Black powder is pretty inefficient stuff. It takes a lot of it to produce a desirable velocity. This means that cartridge cases tended to be just the right size so you could load the proper volume of powder and compress it. Smokeless powders are much more efficient so a lot less of them is used. The thing is that black powder is loaded by volume and smokeless powders are loaded by weight, and this distinction was lost on many reloaders at the dawn of the smokeless era. If you made the mistake of measuring smokeless powder by volume you were probably going to blow up your gun.
When the transition to smokeless powder was made they formulated loads that worked in existing guns. I hear concerns about the excessive pressure and how fast the pressure builds with smokeless powders, but if you use the correct amount of powder this isn’t an issue. Use the correct smaller amount and you’ll get the same pressure as black powder, and pressure is what provides propulsive force. As to how fast that pressure builds no smokeless powder I am aware of burns as fast as black powder, but that does not mean they don’t build up pressure as fast or faster, so caution is called for. They are after all much, much more efficient than black powder. Many of the same powders that were used at the time when they were transitioning to smokeless are still readily available and can be a good place to start. Unique, for example, has proven a good smokeless powder for many black powder cartridges. Red Dot functions well in cases with a smaller capacity, like .32 S&W. Red Dot was scientifically tested a while back, and it has a nearly identical chamber and down-bore pressures as black powder. Of course you use a lot less of it.
The condition and safety of the gun is paramount, not which flavor of propellant you use. Of course any antique firearm should be thoroughly examined by a gunsmith or other qualified person before being fired, and if you value your old guns you’ll keep to mild loads to avoid accelerated wear.
In no small part because of Cowboy Action Shooting all styles of Western-style single-action revolvers have been enjoying a renaissance, including cartridge-conversion guns. With the expiration of S&Ws monopoly on bored-through cylinders Colt was eager to get into the game. They also had literally tons of parts for their cap-and-ball guns, so they did what gunsmiths had already been doing for a few years- they built cap-and-ball guns modified to fire cartridges. There was just enough room to bore through the cylinder of a .44 for a modestly powered cartridge, and shortly thereafter they produced the open-top, which was a purpose built gun rather than a conversion, though it used some components from the earlier guns.
These guns remained popular long after the introduction of the 1873 Single Action Army, in no small part because of the price. A Peacemaker would run you $25, but a Richards-Mason navy conversion revolver would only set you back $5.
There are two ways to get a cartridge-conversion revolver. Nowadays both Taylors and Cimarron offer reproductions of these guns made by Pietta and Uberti in Italy. These are modern, new production firearms and carry no restrictions as to ammunition. They ought to be safe with any standard-pressure ammunition in their caliber, though it would be wise to refrain from using +P ammunition, which will accelerate wear; the open-top frame isn’t the strongest of designs.
The other way to get one is to purchase a cartridge conversion from Kirst or Howells. Both are available as either a replacement cylinder or a gated conversion that requires modification to the frame of the gun. Cap-and-ball revolvers are not made to the same standards as modern cartridge revolvers, but the metallurgy is doubtless at least as good and probably better than the originals. Both Kirst and Howell’s recommend low-pressure ‘cowboy’ loads with lead bullets only. This isn’t because you are likely to blow up the cylinders; these are well constructed modern products. The concern is accelerated wear; quality of reproduction revolvers can vary- best to err on the side of caution.
Both manufacturers state that you should not mount their conversion cylinders in brass-framed revolvers. Most knowledgeable shooters recommend shooting modest loads in these guns, and this is for the same reason that the cylinder manufacturers say not to use them. Brass is much softer than iron or steel, and heavier loads will stretch the frame over time and render the revolver inoperative; sooner or later the frame will stretch enough that the hammer will no longer strike the cap with sufficient force to ignite them, and this is hard to fix. Again, the danger is not so much that the gun will blow up; after all the parts that contain the pressure of firing are steel. It’s the parts that hold them together are the weak link.
Do your own research, educate yourself and proceed with caution and intelligence. There’s a lot of fun to be had with cap-and-ball guns, conversions and antique firearms. With a little common-sense you can have that fun safely- and for a long time.
Michael Tinker Pearce, 20 August 2017