What makes a percussion revolver shoot straight?

Did you ever wonder what makes a percussion revolver shoot straight? What is the difference between a cheap and a more expensive repro? Well, here are the answer you are looking for.

When I decided to start blackpowder shooting, I knew I want a percussion revolver. All my experienced shooter friends told me to start with a single shot percussion pistol or rifle to learn the basics, but I guess blackpowder shooting isn't really about logical decisions so I bought my first 1858 New Model Army revolver in .44 caliber. It was one of the cheaper ones on the market and had some quality issues I did not know by those times. But I was happy even if I could not hit the center of the target with that brass frame Remington. The smoke and the recoil satisfied my need for a real cowboy feel and western gun.

It took me years to understand why this revolver never shot straight. In fact the problems became clear when I bought my Pedersoli Remington Pattern revolver about 12 years ago. The difference was huge I tell you. So here are my thoughts I would like to share with you about the accuracy of percussion revolvers. This small list shows the level where I am now. I know it is not the end of the road, but I hope I can give you a guideline in accurizing your revolver or I can just help you choosing the right revolver if you are before purchasing your first muzzleloading sixshooter.

The mechanics

First let's get into the technical details to understand the basics of percussion revolvers. The things I will write about here were all known by the developers of these arms back in the 19^th century.

The bore

Let's check the bore and the rifling first. First of all it does matter a lot how the rifling is made. The cheaper repros are button rifled. This is done by pressing all grooves at once with a tool called a "button" that is pushed or pulled down the barrel. This is fast and easy way to make a rifling, but for the best accuracy we need something more sophisticated. Pedersoli and all the manufacturers of competition quality percussion arms use a different method: the broach riflilng. This is done with cutting all grooves in one pass with a special progressive broaching bit. But before cutting the grooves the bore is reamed, lapped, straightened for maximum accuracy.

To have competition quality bores this is the only method. It is slow – and more expensive – but offers the best results.

In the 19^th century many of the percussion revolvers were manufactured with gain or progressive twist rifling. The Remingtons and Colts were done like this. This means that the twist rate of the rifling is faster at the muzzle than at the breech. The purpose of the this rifling was simple: when the bullet exited the chamber and reached the forcing cone arrived in a low twist rate part of the bore so it did not deform too much, did not jump the rifling. As it passed thru the bore the twist rate got faster and faster, to have the desired spin as it left the muzzle. I did some – not really accurate - measuring on my original New Model Army manufactured in 1863. I ran a loading rod with a tight fitting patch thru the bore and measured the rate of twist inch by inch. My results show that the twist rate is around 1:60” at the breech and 1:17” at the muzzle. I am sure this data is far from accurate but it is a good indication how it was done. It is possible to recreate this rifling today as well, but it does increase the manufacturing costs tremendously, without increasing the target shooting accuracy. Let's not forget that these revolvers back in the times of the Civil War were meant to fire military revolver cartridges of various types with various bullets and powder loads. The goal of these arms and cartridges were not to hit the center of the target at 25 meters but to punch a hole in a man sized target up to 15 yards.

We are lucky as we can adjust our bullet and powder load freely at the range searching for the top accuracy without the need of killing power. To fire a round ball accurately we don't need too much powder if we have the right rifling twist. A twist rate somewhere between 17-20” will work fine for sure. The faster the twist is the small the charge can be. A low charge means low recoil and improved accuracy.

The forcing cone and the muzzle crown are also very important parts of the bore. If they are not symmetric you can forget the top accuracy. If the muzzle crown is damaged or is off center, the escaping gases will push the bullet leaving the bore to one side. If the forcing cone is not made with proper care it will deform the ball entering the bore.

Selecting the ball size for your revolver

It is said that Remingtons like the .454” balls while Colt's like the .451” bullets. This is absolutely not true. First of all no repro manufacturers use different tools for .44 cal Colts or Remingtons in making the bore. Second your bore determinates the necessary size of the projectile. The barre has two diameters: one you can measure between the grooves and one you can measure between the lands. It is obvious that the groove-to-groove diameter is bigger than the land-to-land diameter. To determinate the exact ball size first you have to slug your barrel. Remove the cylinder and run an oversized greased soft lead ball thru the bore driven by a wooden dowel. The biggest diameter you can measure of the deformed slug will be your groove-to-groove diameter. This is exactly the bullet diameter you will need to have a gas tight fit, and to help the rifling grabbing the bullet effectively.

Controlling the fouling

Another important factor in shooting your revolver accurately is the control of fouling buildup in the bore. A normal competition is 13 (plus one fouling) shots, so you have to make sure that the layer of blackpowder residue in your bore is constant to reach even gas pressures and even muzzle velocities. To reach this goal you need to things: a mirror bright polished bore (in the grooves and on the lands as well), and a good lube. If the bore is not polished well the blackpowder residue will build up faster. If the lube is not working properly the residue will become hard, so the fired balls will not be able to clean the dirt of the previous shot.

The cylinder

OK, we have the good size for the ball. But let's not forget that when we push the bullet into the chamber is shaves off a thin ring, so the diameter of the chamber will also have an effect on accuracy. Now this is a common problem with many of the repros on the market. The chambers tend to have a smaller diameter than what should be necessary in most cases. Imagine a situation when we selected the right size .451” bullet for our bore, but when we load into the chamber it is sized down to .442”. No more gas tight fit, no more accuracy... And this is not a fairy tale. This is what you can actually measure on some repros on the market. If the groove-to-groove diameter is .450” than the chamber diameter has to be at least .450” or rather .451”.

It is also important that the diameter of the chambers has to be absolutely identical. A smaller diameter chamber will hold the bullet stronger than a larger diameter one and this will result a difference in the gas pressures.

The cylinder gap

I see many inexperienced shooters checking the gap between the cylinder and the bore looking for the tightest fit. To tell you the truth it does not matter if this gap is 0,1 or 0,5 mm. What matters is that the distance must be the same with every chamber so the quantity of escaping gases are the same here everytime.

The size of the vent hole of the nipples

The optimal size of the vent hole is between 0,7-0,9 mm on the nipples of a percussion revolver. The smaller the vent hole is, the more ignition problems you can have if you are using lower quality powders. The diameter is important but it is also important that all the nipples must be of the same manufacture with the same size and form vent hole channels.

Indexing

To watch the crescent Moon with the girl you love during a hot summer night by the lake is something we all look for. But to see the same crescent Moon when you watch down the barrel of your cocked – and of course empty – percussion revolver is something that is really painful. The crescent moon is caused by an indexing problem when the chambers do not line completely with the bore. If you are facing this problem you will surely need a good gunsmith to fix it.

The frame

The frame of the repros are manufactured two ways today. The first and older method is using cast steel the second and more precise and stronger way is using hammer forged steel blocks. Pedersoli and Uberti repros are manufactured with forged steel frames. I prefer these.

The trigger work

To place an accurate shot on the target you must have a good control on the trigger. It has to work like a Swiss watch. There are parts of the trigger job you can do at home, but in most cases I recommend you to contact a gunsmith if your trigger pull is too heavy of the trigger does not break. Polishing the surfaces to have a smoother action is something you can also do with fine papers. But to square the engaging surfaces of the sear and hammer is something that must be done by a qualified man. Remember: modifying the trigger pull can make your revolver unsafe. The gunsmith will have the proper tools, knowledge and experience to do this. The competition grade revolvers, like the Pedersoli Remington usually don't need any modification. They will work well out of the box.

Loading your revolver for accuracy

1. Slug your bore to determinate the ball size you need. Stick with roundballs if you go for accuracy use conicals if you g for fun.

2. Check all the points I listed here in this article.

3. Choose a good quality powder brand. Go for the faster burning – 4Fg or 3Fg – powders.

4. Use a moderate powder charge. You don't need more than 18 grains for .44 cal revolver for target shooting.

5. Use filler on the powder – corn meal or felt wad – to lift the bullet to the top of the chamber. If the bullet is seated too deep it will start accelerating in the smooth bore of the cylinder. The bullet lifted to the face of the chamber will immediately reach the forcing cone therefore it will deform less.

6. Use a good quality lubricant on top of the bullet to keep your fouling soft and to avoid chain fires.

This short line of advises will work well on any kind of percussion revolvers regardless of design or maker. But don't forget: the best part in blackpowder shooting is experimenting. So find your own rules, and share the with us what works.