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Rifling

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Rifling of a 105 mmRoyal Ordnance L7tank gun.

Rifling in a.35 Remingtonmicrogroove rifled barrel.

Rifling is the process of makinghelicalgrooves in thebarrelof agunorfirearm, which impartsa spin to aprojectilearound its long axis. This spin serves togyroscopicallystabilize the

projectile, improving itsaerodynamicstability and accuracy.

Rifling is often 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 254 mm"(1:254 mm). A shorter distance indicates a "faster" twist, meaning that for a given velocity theprojectile will be rotating at a higher spin rate.

The combination of length, weight and shape of a projectile determines the twist rate needed to

stabilize itbarrels 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).[1]

Barrels intended for long, small-
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diameter bullets, such as the ultra-low-drag, 80-grain0.223 inch bullets (5.2 g, 5.56 mm), use

twist rates of 1 turn in 8 inches (20 cm) or faster.[2]

In some cases, rifling will have twist rates that increase down the length of the barrel, called a

gain twistorprogressive 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.

[3][4]

Extremely long projectilessuch asflechettesmay require impractically high twist rates; these projectiles must be inherently

stable, and are often fired from asmoothborebarrel.

Contents

1 Historyo 1.1 Recent developments

1.1.1 Polygonal rifling 1.1.2 Extended range, full bore concept 1.1.3 Gain-twist rifling

2 Manufacture 3 Construction and operation 4 Fitting the projectile to the bore 5 Twist rate

o 5.1 Expressing twist rateo 5.2 Twist rate and bullet stabilityo 5.3 Bullet revolutions per minute (rpm)

6 See also 7 References 8 External links

o 8.1 Calculators for stability and twist

History

Traditional rifling of a 9 mm handgun barrel.
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Main article:Rifle

Muskets weresmoothbore, large caliber weapons using ball-shaped ammunition fired at

relatively low velocity. Due to the high cost and great difficulty of precision manufacturing, and

the need to load readily from the muzzle, the musket ball was a loose fit in the barrel.

Consequently on firing the ball bounced off the sides of the barrel when fired and the finaldirection on leaving the muzzle was unpredictable.

Barrel rifling was invented inAugsburg,Germanyat the end of the fifteenth century.[5]In 1520

August Kotter, an armourer of Nuremberg, Germany improved upon this work. Though true

rifling dates from the mid-16th century, it did not become commonplace until the nineteenthcentury.

The concept of stabilizing the flight of a projectile by spinning it was known in the days of bowsand arrows, but early firearms using black powder had difficulty with rifling because of the

fouling left behind by the combustion of the powder. The most successful weapons using rifling

with black powder were breech loaders such as theQueen Anne pistol.

Recent developments

Polygonal rifling

Conventional rifling (left) andpolygonal rifling(right). Both types of rifling use a spiralingpattern.

Main article:Polygonal rifling
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The spiraling pattern (here with normal rifling) is shown.

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 (the grooves are the spaces that are cut out, and the resulting ridges are calledlands) reduces erosion of the barrel. Supporters of polygonal rifling also claim higher velocities

and greater accuracy. Polygonal rifling is currently seen on pistols fromCZ,Heckler & Koch,Glock,Tanfoglio, andKahr Arms, as well as theDesert Eagle.

Extended range, full bore concept

For tanks and artillery pieces, the extended range, full bore concept developed byGerald Bull

for theGC-45 howitzerreverses the normal rifling idea by using a shell with small fins that ridein 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 theSouth AfricanG5and theGermanPzH 2000.

Gain-twist rifling

Gain-twist rifling begins with very little change in the projectile'sangular momentumduring the

first few inches of bullet travel after ignition during the transition fromchamberto throat. This

enables the bullet to remain essentially undisturbed and trued to the case mouth. After engagingthe rifling the bullet is progressively subjected toacceleratedangular momentumas burning

powder propels it down the barrel. By only gradually increasing the spin rate, torque is spread

along a much longer section of barrel, rather than only at the throat where rifling is eroded

through repeated rifling engagement.

Manufacture

Rifling in a French 19th century cannon.

Most rifling is created by either:

cutting one groove at a time with amachine tool(cut rifling or single point cut rifling); cutting all grooves in one pass with a special progressivebroachingbit (broached

rifling);
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pressingall grooves at once with a tool called a "button" that is pushed or pulled downthe barrel (button rifling);

forgingthebarrelover amandrelcontaining a reverse image of the rifling, and often thechamber as well (hammer forging);

flow formingthebarrelpreform over amandrelcontaining a reverse image of the rifling(rifling by flow forming)

The grooves are the spaces that are cut out, and the resulting ridges are called lands. These landsand grooves can vary in number, depth, shape, direction of twist (right or left), and twist rate (see

below). 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, usuallymeasured 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,gunsmithswho aremachininga 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 (seeinternal ballisticsfor 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 rifledbarrel 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 aninternal gear, though it can also

take the shape of apolygon, 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 bedescribed 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 innaming conventions forcartridgescan cause confusion; for example, the projectiles of the.303Britishare actually slightly larger in diameter than the projectiles of 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).

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 projectilesecurely and concentrically as it travels down the barrel. This requires that the rifling meet a

number of tasks:[4]

It must be sized so that the projectile willswageorobturateupon firing to fill the bore. The diameter should be consistent, and must not increase towards the muzzle. The rifling should be consistent down the length of the bore, without changes in cross-

section, such as variations in groove width or spacing.

It should be smooth, with no scratches lying perpendicular to the bore, so it does notabrade material from the projectile.

The chamber and crown must smoothly transition the projectile into and out of the rifling.
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When the projectile is swaged into the rifling, it takes on a mirror image of the rifling, as the

lands push into the projectile in a process called engraving. Engraving takes on not only themajor 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 inforensic ballistics.

Fitting the projectile to the bore

Three recovered7.62x51mm NATObullets (next to an unfired cartridge), showing rifling marks

Russian 122 mm shrapnel shell (which has been fired) showing rifling marks on thecopperalloy

driving bandaround its base
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Cannonballequipped with winglets for rifled cannons circa 1860

Ogival shell of theLa Hitte system, 1858

The original firearms wereloaded from the muzzleby forcing a ball from the muzzle to the

chamber. Whether using a rifled or smooth bore, a good fit was needed to seal the bore andprovide 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 ofsealing, kept the ball seated on the charge ofblack 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
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bullet, as the patch is engraved rather than the ball. Until the advent of the hollow-base Mini

ball, which obturates upon firing to seal the bore and engage the rifling, the patch provided thebest means of getting the projectile to engage the rifling.[6]

Inbreech-loading firearms, the task of seating the projectile into the rifling is handled by the

throatof thechamber. Next is thefreebore, which is the portion of the throat down which theprojectile 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 diameterof 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 chamberpressures low by allowing the propellant gases to expand before being required to engrave the

projectile. Minimizing freebore improves accuracy by decreasing the chance that a projectile willdistort before entering the riffling.[7][8]

Twist rate

For best performance, the barrel should have a twist rate sufficient to spin stabilize anybullet

that it would reasonably be expected to fire, but not significantly more. Large diameter bullets

provide more stability, as the larger radius provides moregyroscopic inertia, while long bullets

are harder to stabilize, as they tend to be very backheavy and the aerodynamic pressures have alonger "lever" to act on. The slowest twist rates are found inmuzzleloadingfirearms meant to

fire a round ball; these will have twist rates as low as 1 in 72 inches (1,800 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. TheM16A2rifle, which is designed to fire the5.56x45mm NATO

SS109 ball and L110 tracerbullets, has a 1 in 7-inch (177.8 mm) or 32 calibers twist. Civilian

AR-15rifles are commonly found with 1 in 12 inches (304.8 mm) or 54.8 calibers for older rifles

and 1 in 9 inches (228.6 mm) or 41.1 calibers for most newer rifles, although some are madewith 1 in 7 inches (177.8 mm) or 32 calibers twist rates, the same as used for the M16 rifle.

Rifles, which generally fire longer, smaller diameter bullets, will in general have faster twist

rates than handguns, which fire shorter, larger diameter bullets.

Expressing twist rate

Three methods are used to describe the twist rate.

The first and traditionally most common method expresses the twist rate in the length required to

complete one full projectile revolution in the rifled barrel.This method does not give an easy understanding if a twist rate is relatively slow or fast when

bores of different diameters are compared.
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The second method describes the length required to complete one full projectile revolution in

calibers or bore diameters.

where:

Twist = twist rate expressed in bore diameters L = the twist length required to complete one full projectile revolution in mm or in Dbore = bore diameter (diameter of the lands) in mm or in

The third method describes the angle of the grooves relative to the bore axis in degrees.The last two methods have the advantage that they express the twist rate as a ratio and give an

easy understanding if a twist rate is relatively slow or fast even when comparing bores of

differing diameters.

Twist rate and bullet stability

In 1879,George Greenhill, a professor of mathematics at theRoyal Military Academy (RMA) at

Woolwich, London, UK[9]developed arule of thumbfor calculating the optimal twist rate for

lead-core bullets. This shortcut uses the bullet's length, needing no allowances for weight or nose

shape.[10]

The eponymous Greenhill Formula, still used today, is:

where:

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'sspecific 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 of600 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 25, which means 1 turn in 25 inches (640 mm).

Improved formulas for determining stability and twist rates include theMiller Twist Rule[11]

and

theMcGyroprogram[12]

developed by Bill Davis and Robert McCoy.
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AParrott rifle, used by bothConfederateandUnionforces in theAmerican Civil War.

If an insufficient twist rate is used, the bullet will begin toyawand then tumble; this is usuallyseen 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 itprecesses.

Conversely, too-high a rate of twist can also cause problems. The excessive twist can cause

accelerated barrel wear, and coupled with high velocities also induce a very high spin rate whichcan cause projectilejacketruptures causing high velocity spin stabilized projectiles todisintegrate in flight. Spin stabilized projectiles made out of mono metals can practically not

obtain adequate flight and spin velocities to disintegrate in flight due to their spin rate.[13]

Smokeless powdercan produce muzzle velocities of approximately 1,600 m/s (5,200 ft/s) forspin stabilized projectiles and more advanced propellants used insmoothboretank guns can

produce muzzle velocities of approximately 1,800 m/s (5,900 ft/s).[14]

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. Undersizedbullets also have problems, as they may not enter the rifling exactlyconcentricandcoaxialto the

bore, and excess twist will exacerbate the accuracy problems this causes. Lastly, a bullet which is

"overstabilized" will maintain the orientation it was fired at; aballistic trajectoryrequires the gunto be aimed above the target, thus an overstabilized bullet at long range will be pointing upward,

even though it is moving downward, resulting in an oblique impact and aerodynamic

inefficiency. Ideally, a spin stabilized bullet is stable enough to not tumble, but unstable enoughto allowaerodynamic forcesto cause the tip to always point in the direction of travel.

Bullet revolutions per minute (rpm)

A bullet fired from a rifled barrel can spin at over 300,000rpm, depending on the bullet'smuzzle

velocity (MV) and the barrel'stwist rate.

The general formula for calculating therpmof a rotating object may be written as
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11/12

where is the linearvelocityof a point in the rotating object (in units of distance/minute) and C

refers to the circumference of the circle that this measuring point performs around the axis ofrotation.

For a bullet, the specific formula below uses the bullet's MV and the barrel's twist rate to

calculate rotational speed:

MV(in fps) x (12/twist rate in inches) x 60 = Bullet rpmFor example, a bullet with a muzzle velocity of 3050 ft/s fired from a barrel with a twist rate of 1in 7-inch (180 mm) (e.g., the M16A2 rifle) spins at 313,714 rpm.

[15]

Excessive rotational speed can exceed the bullet's designed limits and the resulting centrifugalforce can cause the bullet to disintegrate in a radial fashion.[16]

See also

Rifle Smoothbore Paradox gun Comparison microscope Gun barrel sequence (James Bond) Greenhill formula Glossary of firearms terminology Miller twist rate

References1. ^Randy D. Smith."The .54 Caliber Muzzleloader". Chuck Hawks.2. ^"Products::Rifle Barrels::Calibers and Twists". Shilen Rifles, Inc..3. ^"gain twist". MidwayUSA GunTec Dictionary.4. ^abDan Lilja."What makes a barrel accurate?".5. ^W. S. Curtis."Long Range Shooting: A Historical Perspective".6. ^Sam Fadala (2006). The Complete Blackpowder Handbook: The Latest Guns and Gear.

Gun Digest.ISBN0-89689-390-1. Chapter 18, The Cloth Patch

7. ^P. O. Ackley (1966).Handbook for Shooters & Reloaders Volume II. Plaza Publishing.pages 97-98

8.

^Daniel Lilja."Thoughts on Throats for the 50 BMG".9. ^School of Mathematics and Statistics, University of St Andrews, Scotland.AlfredGeorge Greenhill (October 2003) .http://www-history.mcs.st-

andrews.ac.uk/~history/Biographies/Greenhill.html 10.^Mosdell, Matthew. The Greenhill

Formula.http://www.mamut.net/MarkBrooks/newsdet35.htm (Accessed 2009 AUG 19)

11.^Miller, Don.How Good Are Simple Rules For Estimating Rifling Twist, PrecisionShooting - June 2009
http://en.wikipedia.org/wiki/Velocityhttp://en.wikipedia.org/wiki/Velocityhttp://en.wikipedia.org/wiki/Velocityhttp://en.wikipedia.org/wiki/Rifling#cite_note-15http://en.wikipedia.org/wiki/Rifling#cite_note-15http://en.wikipedia.org/wiki/Rifling#cite_note-15http://en.wikipedia.org/wiki/Rifling#cite_note-16http://en.wikipedia.org/wiki/Rifling#cite_note-16http://en.wikipedia.org/wiki/Rifling#cite_note-16http://en.wikipedia.org/wiki/Riflehttp://en.wikipedia.org/wiki/Riflehttp://en.wikipedia.org/wiki/Smoothborehttp://en.wikipedia.org/wiki/Smoothborehttp://en.wikipedia.org/wiki/Paradox_gunhttp://en.wikipedia.org/wiki/Paradox_gunhttp://en.wikipedia.org/wiki/Comparison_microscopehttp://en.wikipedia.org/wiki/Comparison_microscopehttp://en.wikipedia.org/wiki/Gun_barrel_sequence_%28James_Bond%29http://en.wikipedia.org/wiki/Gun_barrel_sequence_%28James_Bond%29http://en.wikipedia.org/wiki/Greenhill_formulahttp://en.wikipedia.org/wiki/Greenhill_formulahttp://en.wikipedia.org/wiki/Glossary_of_firearms_terminologyhttp://en.wikipedia.org/wiki/Glossary_of_firearms_terminologyhttp://en.wikipedia.org/wiki/Miller_twist_ratehttp://en.wikipedia.org/wiki/Miller_twist_ratehttp://en.wikipedia.org/wiki/Rifling#cite_ref-1http://en.wikipedia.org/wiki/Rifling#cite_ref-1http://www.chuckhawks.com/54_caliber_muzzleloader.htmhttp://www.chuckhawks.com/54_caliber_muzzleloader.htmhttp://www.chuckhawks.com/54_caliber_muzzleloader.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-2http://www.shilen.com/calibersAndTwists.htmlhttp://www.shilen.com/calibersAndTwists.htmlhttp://www.shilen.com/calibersAndTwists.htmlhttp://en.wikipedia.org/wiki/Rifling#cite_ref-3http://www.midwayusa.com/guntecdictionary.exe/showterm?TermID=2535http://www.midwayusa.com/guntecdictionary.exe/showterm?TermID=2535http://www.midwayusa.com/guntecdictionary.exe/showterm?TermID=2535http://en.wikipedia.org/wiki/Rifling#cite_ref-lilja_accurate_4-0http://en.wikipedia.org/wiki/Rifling#cite_ref-lilja_accurate_4-0http://en.wikipedia.org/wiki/Rifling#cite_ref-lilja_accurate_4-1http://en.wikipedia.org/wiki/Rifling#cite_ref-lilja_accurate_4-1http://en.wikipedia.org/wiki/Rifling#cite_ref-lilja_accurate_4-1http://riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htmhttp://riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htmhttp://riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-5http://en.wikipedia.org/wiki/Rifling#cite_ref-5http://www.lrml.org/historical/longrange/history02.htmhttp://www.lrml.org/historical/longrange/history02.htmhttp://www.lrml.org/historical/longrange/history02.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-6http://en.wikipedia.org/wiki/Rifling#cite_ref-6http://en.wikipedia.org/wiki/International_Standard_Book_Numberhttp://en.wikipedia.org/wiki/International_Standard_Book_Numberhttp://en.wikipedia.org/wiki/Special:BookSources/0-89689-390-1http://en.wikipedia.org/wiki/Special:BookSources/0-89689-390-1http://en.wikipedia.org/wiki/Special:BookSources/0-89689-390-1http://en.wikipedia.org/wiki/Rifling#cite_ref-7http://en.wikipedia.org/wiki/Rifling#cite_ref-7http://en.wikipedia.org/wiki/Rifling#cite_ref-8http://en.wikipedia.org/wiki/Rifling#cite_ref-8http://www.riflebarrels.com/articles/50calibre/throats_50_bmg.htmhttp://www.riflebarrels.com/articles/50calibre/throats_50_bmg.htmhttp://www.riflebarrels.com/articles/50calibre/throats_50_bmg.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-9http://en.wikipedia.org/wiki/Rifling#cite_ref-9http://www-history.mcs.st-andrews.ac.uk/~history/Biographies/Greenhill.htmlhttp://www-history.mcs.st-andrews.ac.uk/~history/Biographies/Greenhill.htmlhttp://www-history.mcs.st-andrews.ac.uk/~history/Biographies/Greenhill.htmlhttp://www-history.mcs.st-andrews.ac.uk/~history/Biographies/Greenhill.htmlhttp://en.wikipedia.org/wiki/Rifling#cite_ref-10http://en.wikipedia.org/wiki/Rifling#cite_ref-10http://en.wikipedia.org/wiki/Rifling#cite_ref-10http://www.mamut.net/MarkBrooks/newsdet35.htmhttp://www.mamut.net/MarkBrooks/newsdet35.htmhttp://www.mamut.net/MarkBrooks/newsdet35.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-11http://en.wikipedia.org/wiki/Rifling#cite_ref-11http://en.wikipedia.org/wiki/Rifling#cite_ref-11http://www.jbmballistics.com/bibliography/articles/miller_stability_2.pdfhttp://www.jbmballistics.com/bibliography/articles/miller_stability_2.pdfhttp://www.jbmballistics.com/bibliography/articles/miller_stability_2.pdfhttp://www.jbmballistics.com/bibliography/articles/miller_stability_2.pdfhttp://en.wikipedia.org/wiki/Rifling#cite_ref-11http://www.mamut.net/MarkBrooks/newsdet35.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-10http://www-history.mcs.st-andrews.ac.uk/~history/Biographies/Greenhill.htmlhttp://www-history.mcs.st-andrews.ac.uk/~history/Biographies/Greenhill.htmlhttp://en.wikipedia.org/wiki/Rifling#cite_ref-9http://www.riflebarrels.com/articles/50calibre/throats_50_bmg.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-8http://en.wikipedia.org/wiki/Rifling#cite_ref-7http://en.wikipedia.org/wiki/Special:BookSources/0-89689-390-1http://en.wikipedia.org/wiki/International_Standard_Book_Numberhttp://en.wikipedia.org/wiki/Rifling#cite_ref-6http://www.lrml.org/historical/longrange/history02.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-5http://riflebarrels.com/articles/barrel_making/rifle_barrel_accurate.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-lilja_accurate_4-1http://en.wikipedia.org/wiki/Rifling#cite_ref-lilja_accurate_4-0http://www.midwayusa.com/guntecdictionary.exe/showterm?TermID=2535http://en.wikipedia.org/wiki/Rifling#cite_ref-3http://www.shilen.com/calibersAndTwists.htmlhttp://en.wikipedia.org/wiki/Rifling#cite_ref-2http://www.chuckhawks.com/54_caliber_muzzleloader.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-1http://en.wikipedia.org/wiki/Miller_twist_ratehttp://en.wikipedia.org/wiki/Glossary_of_firearms_terminologyhttp://en.wikipedia.org/wiki/Greenhill_formulahttp://en.wikipedia.org/wiki/Gun_barrel_sequence_%28James_Bond%29http://en.wikipedia.org/wiki/Comparison_microscopehttp://en.wikipedia.org/wiki/Paradox_gunhttp://en.wikipedia.org/wiki/Smoothborehttp://en.wikipedia.org/wiki/Riflehttp://en.wikipedia.org/wiki/Rifling#cite_note-16http://en.wikipedia.org/wiki/Rifling#cite_note-15http://en.wikipedia.org/wiki/Velocity


12/12

12.^http://www.jbmballistics.com/downloads/text/mcgyro.txt 13.^THE 22x64 EXPERIMENT Shooting meat for the freezer at 1,433 m/s (4,700 ft/s)14.^"120mm Tank Gun KE Ammunition". Defense Update. 2006-11-22. Retrieved 2007-

09-03.

15.^[1]Calculating Bullet RPM16.

^[2]Twist Rate
http://en.wikipedia.org/wiki/Rifling#cite_ref-12http://en.wikipedia.org/wiki/Rifling#cite_ref-12http://www.jbmballistics.com/downloads/text/mcgyro.txthttp://www.jbmballistics.com/downloads/text/mcgyro.txthttp://www.jbmballistics.com/downloads/text/mcgyro.txthttp://en.wikipedia.org/wiki/Rifling#cite_ref-13http://en.wikipedia.org/wiki/Rifling#cite_ref-13http://www.gsgroup.co.za/22x64.htmlhttp://www.gsgroup.co.za/22x64.htmlhttp://www.gsgroup.co.za/22x64.htmlhttp://en.wikipedia.org/wiki/Rifling#cite_ref-14http://en.wikipedia.org/wiki/Rifling#cite_ref-14http://www.defense-update.com/products/digits/120ke.htmhttp://www.defense-update.com/products/digits/120ke.htmhttp://www.defense-update.com/products/digits/120ke.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-15http://en.wikipedia.org/wiki/Rifling#cite_ref-15http://accurateshooter.wordpress.com/2008/06/03/calculating-bullet-rpm-spin-rates-and-stability/http://accurateshooter.wordpress.com/2008/06/03/calculating-bullet-rpm-spin-rates-and-stability/http://accurateshooter.wordpress.com/2008/06/03/calculating-bullet-rpm-spin-rates-and-stability/http://en.wikipedia.org/wiki/Rifling#cite_ref-16http://en.wikipedia.org/wiki/Rifling#cite_ref-16http://www.loadammo.com/Topics/July01.htmhttp://www.loadammo.com/Topics/July01.htmhttp://www.loadammo.com/Topics/July01.htmhttp://www.loadammo.com/Topics/July01.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-16http://accurateshooter.wordpress.com/2008/06/03/calculating-bullet-rpm-spin-rates-and-stability/http://en.wikipedia.org/wiki/Rifling#cite_ref-15http://www.defense-update.com/products/digits/120ke.htmhttp://en.wikipedia.org/wiki/Rifling#cite_ref-14http://www.gsgroup.co.za/22x64.htmlhttp://en.wikipedia.org/wiki/Rifling#cite_ref-13http://www.jbmballistics.com/downloads/text/mcgyro.txthttp://en.wikipedia.org/wiki/Rifling#cite_ref-12

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