.......October 2008 ~~~~ Editor:  Cliff Hanger ~~~~
Don't Forget
Last Stand at Chimney Rock / SASS Western Regional starts in one week.  Octber 9th - 12th.  Info and Entry Form
Chimney Rock had been quiet,

almost too quiet in the time since the last big mineral cycle caused the town to boom, with violent results. But now, the easy money was gone from the town and gone too were most of the bad men and wild women that bring a colorful, if sometimes raucous energy to a town.

But like the storm clouds building up in the mountains there was a change building in the town. An old miner, exploring his played out claim had chanced upon some strange symbols cut into freshly exposed rock, a box with a cross above it and a triangle in a circle. With further investigation the old miner found a small strong box with an old pistol with a J carved into the grips, a quantity of gold and silver coins, a journal and some strangely marked maps.

The old miner was cagey but he couldn't read. So he hid most of the gold and most of the maps and took the pistol and the journal back to town to get
someone to read from it in hopes of finding out more about this strange find. Little did the old miner suspect that the journal he had found belonged to none other than Jesse James and the markers and the maps held the keys to a Civil War treasure, hidden in the hills by members of the Knights of the Golden Circle, a Southern group who were known to have hidden money and arms throughout the South and Southwest in order for the Confederacy to take over Northern Mexico, and later to keep the hopes of the South alive in the waning days of the conflict with the North.

The only person the old miner knew could read in the town of Chimney rock was Thomas Francis Shelby, a barber and dentist from Missouri who had fought in the civil war and who knew the meaning of the symbols and the importance of the journal as soon as the Old miner showed them to him. Convincing the old man to show him the symbols T. F. Shelby accompanied the miner to his old claim and upon seeing the marks in the rocks shot the old man in the back, leaving him to die in the hills. 

While Shelby rode back to Chimney Rock, the old miner, tougher than he looked dragged himself up toward his old cabin. Before getting there he was
found by a passing stranger and the old man told him his story and knowing he was about to die, trusted him with the secret of the maps and asked the
stranger to make sure that he was buried proper and that the money, if there was any was sent to his daughter he had left behind back in St. Louis.

The stranger promised the old miner that his wishes would be met and after he buried him and located the maps, the stranger went down to town to serve

Meanwhile, Shelby had been burning up the telegraph wires, contacting relatives and shadowy men who begin the trip to Chimney Rock and the promise
of treasure, and violence. Once again it seemed that Chimney Rock was to be the site of a clash of wills and witness to the flash, smoke and thunder of
a battle.

(Hand bills posted all over town)
A Promise, I aim to keep.

Good men of Chimney Rock! I need your help to keep a promise I made to an old local miner I found shot in the back. I'll explain on Nov. 30th in front of the Chimney Rock Depot. 

All over the western frontier the telegraph operators were receiving and delivering short to the point telegram,

"Come at once. (stop)
Gold and Silver to be had.  (stop)
Ride hard and heeled. (stop)
In Chimney Rock, Nov. 30th" (stop)
Thomas Francis Shelby (stop)

Choose a side and get to Chimney Rock!  November 30th. 

"Thunder Valley" 2008 an all black powder match 

Details have been finalized . . . . . . the 6 stages are being tweaked here and there but we're ready. 
All the information can be found here.  Category Requirements & Entry Form

Remember at this match you can choose to enter two categories if you really want to do a lot of shooting.  12 Stages of black powder! 
The main match will cost you $30.00. If you pre register by Nov. 22nd., it will include your lunch. For $15.00 more you can shoot two categories.  If you decide to just show up on match day, Come on, you'll be Welcome. Lunch will cost ya an additional $5.00.

Rifling from Wikipedia

Rifling refers to the helix-shaped pattern in the barrel of a firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.

Rifling is described by its twist rate, which indicates the distance the bullet must travel to complete one full revolution, such as "1 turn in 10 inches" (1:10 inches), or "1 turn in 30 cm" (1:30 cm). A shorter distance indicates a "faster" twist, meaning that for a given velocity the projectile will be rotating at a higher spin rate.

The length of a projectile determines the twist rate needed to stabilize it - barrels intended for short, large-diameter projectiles like spherical lead balls require a very low twist rate, such as 1 turn in 48 inches (122 cm). Barrels intended for long, small-diameter bullets, such as the ultra-low-drag, 80-grain 0.224 inch bullets (5.2 g, 5.56 mm), use twist rates of 1 turn in 8 inches (20 cm) or faster.

In some cases, rifling will have twist rates that increases down the length of the barrel, called a gain twist; a twist rate that decreases from breech to muzzle is undesirable, as it cannot reliably stabilize the bullet as it travels down the bore. Extremely long projectiles such as flechettes may require impractically high twist rates; these projectiles must be inherently stable, and are often fired from a smoothbore barrel.

Rifling of a Canon de 75 modèle 1897

Rifling in a .35 Remington microgroove rifled barrel
Most rifling is created by either:

    * cutting one groove at a time with a machine tool (cut rifling or single point cut rifling);
    * cutting all grooves in one pass with a special progressive broaching bit (broached rifling);
    * pressing all grooves at once with a tool called a "button" that is pushed or pulled down the barrel
(button rifling);
    * forging the barrel over a mandrel containing a reverse image of the rifling, and often the chamber as well (hammer forging);
    * flow forming the barrel preform over a mandrel containing a reverse image of the rifling 
(rifling by flow forming)

Rifling in a French 19th century cannon
The grooves are the spaces that are cut out, and the resulting ridges are called "lands". These lands and grooves can vary in number, depth, shape, direction of twist ("right" or "left"), and "twist rate" (turns per unit of barrel length). The spin imparted by rifling significantly improves the stability of the projectile, improving both range and accuracy. Typically rifling is a constant rate down the barrel, usually measured by the length of travel required to produce a single turn. Occasionally firearms are encountered with a gain twist, where the rate of spin increases from chamber to muzzle. While intentional gain twists are rare, due to manufacturing variance, a slight gain twist is in fact fairly common. Since a reduction in twist rate is very detrimental to accuracy, gunsmiths who are machining a new barrel from a rifled blank will often measure the twist carefully so they may put the faster rate, no matter how minute the difference is, at the muzzle end (see internal ballistics for more information on accuracy and bore characteristics).

Construction and operation.

A barrel of circular cross-section is not capable of imparting a spin to a projectile, so a rifled barrel has a non-circular cross-section. Typically the rifled barrel contains one or more grooves that run down its length, giving it a cross-section resembling a gear, though it can also take the shape of a polygon, usually with rounded corners. Since the barrel is not circular in cross-section, it cannot be accurately described with a single diameter. Rifled bores may be described by the bore diameter (the diameter across the lands or high points in the rifling), or by groove diameter (the diameter across the grooves or low points in the rifling.) Differences in naming conventions for cartridges can cause confusion; for example, the .303 British is actually slightly larger in diameter than the .308 Winchester, because the ".303" refers to the bore diameter in inches, while the ".308" refers to the groove diameter in inches (7.70 mm and 7.82 mm, respectively.)
Conventional rifling (left) and polygonal rifling (right)

More on Polygonal Rifling to follow this article

Despite differences in form, the common goal of rifling is to deliver the projectile accurately to the target. In addition to imparting the spin to the bullet, the barrel must hold the projectile securely and concentrically as it travels down the barrel. This requires that the rifling meet a number of tasks:[4]

   1. It must be sized so that the projectile will swage or obturate upon firing to fill the bore.
   2. The diameter should be consistent, and must not increase towards the muzzle.
   3. The rifling should be consistent down the length of the bore, without changes in cross-section, such as variations in groove width or spacing.
   4. It should be smooth, with no scratches lying perpendicular to the bore, so it does not abrade material from the projectile.
   5. The chamber and crown must smoothly transition the projectile into and out of the rifling.

When the projectile is swaged into the rifling, it takes on a mirror image of the rifing, as the lands push into the projectile in a process called engraving. Engraving takes on not only the major features of the bore, such as the lands and grooves, but also minor features, like scratches and tool marks. The relationship between the bore characteristics and the engraving on the projectile are often used in forensic ballistics.

Fitting the projectile to the bore

The original firearms were loaded from the muzzle by forcing a ball from the muzzle to the breech. Whether using a rifled or smooth bore, a good fit was needed to seal the bore and provide the best possible accuracy from the gun. To ease the force required to load the projectile, these early guns used an undersized ball, and a patch made of cloth, paper, or leather to fill the windage (the gap between the ball and the walls of the bore.) The patch provided some degree of sealing, kept the ball seated on the charge of black powder, and kept the ball concentric to the bore. In rifled barrels, the patch also provided a means to transfer the spin from the rifling to the bullet, as the patch is engraved rather than the ball. Until the advent of the hollow-base Minié ball, which obturates upon firing to seal the bore and engage the rifling, the patch provided the best means of getting the projectile to engage the rifling.

In breech-loading firearms, the task of seating the projectile into the rifling is handled by the throat of the chamber. Next is the freebore, which is the portion of the throat down which the projectile travels before the rifling starts. The last section of the throat is the throat angle, where the throat transitions into the rifled barrel.

The throat is usually sized slightly larger than the projectile, so the loaded cartridge can be inserted and removed easily, but the throat should be as close as practical to the groove diameter of the barrel. Upon firing, the projectile expands under the pressure from the chamber, and obturates to fit the throat. The bullet then travels down the throat and engages the rifling, where it is engraved, and begins to spin. Engraving the projectile requires a significant amount of force, and in some firearms there is a significant amount of freebore, which helps keep chamber pressures low by allowing the propellant gases to expand before being required to engrave the projectile. Best accuracy, however, is typically provided with a minimum of freebore, maximizing the changes that the projectile will enter the rifling without distortion.

Twist rate

For best performance, the barrel should have a twist rate sufficient to stabilize any bullet that it would reasonably be expected to fire, but not significantly more. Large diameter bullets provide more stability, as the larger radius provides more gyroscopic inertia, while long bullets are harder to stabilize, as they tend to be very backheavy and the aerodynamic pressures have a longer "lever" to act on. The slowest twist rates are found in muzzleloading firearms meant to fire a round ball; these will have twist rates as low as 1 in 60 inches (1,500 mm), or slightly longer, although for a typical multi-purpose muzzleloader rifle, a twist rate of 1 in 48 inches (1,200 mm) is very common. The M16A2 rifle, which is designed to fire the SS109 bullet, has a 1 in 7-inch (180 mm) twist. Civilian AR-15 rifles are commonly found with 1 in 12 inches (300 mm) for older rifles and 1 in 9 inches (230 mm) for most newer rifles, although some are made with 1 in 7 inches (180 mm) twist rates, the same as used for the M16. Rifles, which generally fire longer, smaller diameter bullets, will in general have higher twist rates than handguns, which fire shorter, larger diameter bullets.

George Greenhill, a mathematician at Emmanuel College, Cambridge, UK, developed a rule of thumb for use in calculating twist rates for a given lead-core bullet. The formula, named the Greenhill Formula in his honour, is:

    * C = 150 (use 180 for muzzle velocities higher than 2,800 f/s)
    * D = bullet's diameter in inches
    * L = bullet's length in inches
    * SG = bullet's specific gravity (10.9 for lead-core bullets, which cancels out the second half of the equation)

The original value of C was 150, which yields a twist rate in inches per turn, when given the diameter D and the length L of the bullet in inches. This works to velocities of about 840 m/s (2800 ft/s); above those velocities, a C of 180 should be used. For instance, with a velocity of 600 m/s (2000 ft/s), a diameter of 0.5 inches (13 mm) and a length of 1.5 inches (38 mm), the Greenhill formula would give a value of 30, which means 1 turn in 30 inches (760 mm).

If an insufficient twist rate is used, the bullet will begin to yaw and then tumble; this is usually seen as "keyholing", where bullets leave elongated holes in the target as they strike at an angle. Once the bullet starts to yaw, any hope of accuracy is lost, as the bullet will begin to veer off in random directions as it precesses.

Conversely, too-high a rate of twist can also cause problems. The excessive twist can cause accelerated barrel wear, and also induce a very high spin rate which can cause high-velocity projectiles to disintegrate in flight. A higher twist than needed can also cause more subtle problems with accuracy: Any inconsistency within the bullet, such as a void that causes an unequal distribution of mass, may be magnified by the spin. Undersized bullets also have problems, as they may not enter the rifling exactly concentric and coaxial to the bore, and excess twist will exacerbate the accuracy problems this causes. Lastly, excessive spinning causes a reduction in the lateral kinetic energy of a projectile, thereby reducing its destructive power (the energy instead becomes rotational kinetic energy).

A Parrott rifle, used by both Confederate and Union forces in the American Civil War
Recent developments

The grooves most commonly used in modern rifling have fairly sharp edges. More recently, polygonal rifling, a throwback to the earliest types of rifling, has become popular, especially in handguns. Polygonal barrels tend to have longer service lives because the reduction of the sharp edges of the land reduces erosion of the barrel. Supporters of polygonal rifling also claim higher velocities and greater accuracy. Polygonal rifling is currently seen on pistols from Heckler & Koch, Glock and Kahr Arms, as well as the Desert Eagle.

For tanks and artillery pieces, the extended range, full bore concept developed by Gerald Bull for the GC-45 howitzer reverses the normal rifling idea by using a shell with small fins that ride in the grooves, as opposed to using a slightly oversized projectile which is forced into the grooves. Such guns have achieved significant increases in muzzle velocity and range. Examples include the South African G5 and the German PzH 2000.

Polygonal rifling from Wikipedia

Polygonal rifling is a type of rifling wherein the traditional lands and grooves are replaced by "hills and valleys" in a rounded polygonal pattern, usually a hexagon.

Conventional eight groove rifling on the left, and octagonal polygonal rifling on the right

While polygonal rifling has been around since the earliest days of rifled barrels, it had faded out of use by the time of the early cordite cartridges. The last common rifle to use polygonal rifling was the Lee-Metford rifle, named after the Metford rifling, a 7 sided polygonal type rifling. The switch to cordite from black powder proved too much for the shallow rifling in the relatively soft barrels of the time, and the Lee-Metford became the Lee-Enfield when the Metford rifling was dropped. Heckler & Koch was the first manufacturer to begin using polygonal rifling in modern arms. Companies that utilize this method today include Heckler & Koch, Glock, Magnum Research, Noveske Rifleworks and Kahr Arms. Polygonal rifling is usually only found in pistol barrels, and is less common in rifles, However some extremely high end rifles like the PSG-1 use polygonal bores.

The term "polygonal rifling" is fairly general, and different manufacturers employ varying polygonal rifling profiles.


A number of advantages are claimed by the supporters of polygonal rifling. These include:

    * Higher velocities due to reduced friction of the bullet in the barrel, as the polygonal rifling has less surface area than the lands and grooves of a traditionally rifled barrel
    * Less bullet deformation, resulting in reduced drag on the bullet which helps to increase range and accuracy
    * Increased barrel life and reduced buildup of copper or lead within the barrel

However, precision target pistols such as those used in bullseye and IHMSA almost universally use traditional rifling, as do target rifles. The debate among target shooters is almost always one of cut vs. button rifled barrels, as traditional rifling is dominant. Polygonal rifled barrels are used competitively in pistol action shooting, such as IDPA and IPSC competitions.

Part of the difference may be that most polygonal rifling is produced by hammer forging the barrel around a mandrel containing a reverse impression of the rifling. Hammer forging machines are tremendously expensive, far out of the reach of custom gunsmiths (unless they buy pre-rifled blanks), and so are generally only used for production barrels by large companies. The main advantage of a hammer forging process is that it can rifle, chamber, and contour a bored barrel blank in one step. First applied to gun barrel rifling in Germany in 1939, hammer forging has remained popular in Europe, but was only later used by gunmakers in the United States. The hammer forging process produces large amounts of stress in the barrel that must be relieved by careful heat treatment, a process that is less necessary in a traditionally cut or button rifled barrel. Due to the potential for residual stress causing accuracy problems, precision shooters tend to avoid hammer forged barrels, and this limits them in the type of available rifling.

Lead bullets and polygonal rifling

The manufacturer Glock advises against using lead bullets (meaning bullets not covered by a copper jacket) in their polygonally rifled barrels, which has led to a widespread belief that polygonal rifling is not compatible with lead bullets. Noted firearms expert and barrel maker, the late Gale McMillan, has also commented that lead bullets and polygonal rifling are not a good mix. However, since neither H&K nor Kahr recommend against lead bullets in their polygonal rifled barrels, it is probable that there is an additional factor involved in Glock's warning. One explanation is that Glock barrels have a fairly sharp transition between the chamber and the rifling, and this area is prone to lead buildup if lead bullets are used. This buildup may result in failures to fully return to battery, allowing the gun to fire with the case not fully supported by the chamber, leading to a potentially dangerous case failure. The other explanation is that Glock's barrels may be more prone than normal to leading, which is the buildup of lead in the bore that happens in nearly all firearms firing high velocity lead bullets. This lead buildup must be cleaned out regularly, or the barrel can become constricted and result in higher than normal pressures.

All articles submitted to the "Brimstone Gazette" are the property of the author, used with their expressed permission. 
The Brimstone Pistoleros are not responsible for any accidents which may occur from use of  loading data, firearms information, or recommendations published on the Brimstone Pistoleros web site.