Choosing a rifle calibre


Choosing a calibre To start with, the term calibre simply refers to the diameter of the bullet and the corresponding hole through the barrel. The designation of a calibre, eg 7.62x51mm, means that the bullet is 7.62mm in diameter (or the rifle bore it is designed for is 7.62mm, it depends whether you measure across the grooves or the lands of the barrel). The second number refers to the length of the brass case the bullet is seated in. For example, we can tell by looking at the .30-06 (or 7.62x63mm) and the .308 (or 7.62x51mm) that the rounds are broadly similar but the .30-06 has a much longer case. Choosing a calibre can be quite a bewildering task and really depends on what you intend to shoot - varmints, game or targets? Many calibres have various uses - the .308 Winchester is used for hunting and target shooting all over the world. Other calibres are generally just used for specific tasks - the relatively new .204 Ruger, for example, tends to be used for pest control exclusively; it is a popular foxing calibre in the UK. One thing very noticeable if you study the bullet weight versus energy figures is that speed is more of a factor than weight. If you double the weight of a projectile for a given velocity you only double the energy. However, if you double the velocity of a projectile for a given weight, the energy is multiplied by 4. The following 14 calibres are commonly used in the UK, the second 14 are less common (or never seen because they are military):



Usually known as the .300 'Whizzum', the .300 Winchester Short Magnum was introduced in 2001 by Winchester in a move towards shorter cartridges based on existing designs, see below. This allows shorter, stiffer actions to be utilised in rifles which is thought to aid accuracy. It typically propels a 165 grain projectile at 3,200 FPS giving 3,800 foot pounds energy.

Also known as the 7.82x67mm, the .300 Win Mag was created by Winchester in 1963 as part of their Magnum range. It is a large game and long range target shooting round. It is used in long range bench-rest shooting competitions and has been adopted by law enforcement professionals and military snipers. It typically propels a 180 grain projectile at 2,950 FPS giving 3,450 foot pounds energy.

Also known as the 7.62x63mm. The .30-06 is a .30 calibre round and was created by the US Military in 1906, hence it's name; it is generally pronounced 'thirty-ought-six'. The .30-06 was predominantly a miltary cartridge and saw action in both rifles and machine guns from the early 1900s until it was phased out in the 1970s when it was superceded by the 7.62x51mm. Nowadays, it is the most popular hunting cartridge in America and is typically loaded with bullets weighing 150-180 grains at velocities of around 2,850 FPS giving 2,800-3,300 foot pounds energy.

Also known as the 7.92x57mm or 8x57mm, both of which are suffixed with I or IS in Europe and J or JS in America. The 8mm Mauser was designed by the German Rifle Commission in 1888 for use in Model 1888 Commission Rifle, or Gewehr 98 (G98). The original 8mm Mauser round was a relatively low pressure cartridge and fired a round-nosed .318 projectile, this was the 7.92x57 I (I standing for infantry). This I was misinterpreted and became the 7.92x57J in America. The cartridge was soon improved to fire a .323" pointed bullet at far greater pressure and was known as the 7.92x57IS, the IS standing for 'Infanterie, Spitz' or 'Infantry, Pointed'. The improved cartridge was famously used in the Gewehr 98 and Karabiner 98k, the standard German infantry rifles of World War 2 as well as the fearsome MG34 and MG42 machine guns. Typically loaded with bullets weighing around 190 grains fired at velocities of 2,700 FPS giving 3,000 foot pounds energy.

Developed by Winchester in 1923, the .270 Win was released in 1925 for their bolt-action Model 54 rifle. Despite the .270 Win being a powerful, flat-shooting round, adoption was initially slow. It is now the second most popular hunting cartridge in the world, after the .30-06 Springfield. Take up in the UK has been slower due the perceived harsh recoil and noise of the cartridge. Recently, the increasingly positive attitude of British Police towards sound moderators (which help reduce recoil) has led to an increase in popularity and the .270 Win is especially popular with deer stalkers for it's long range and punch. A more modern development of this cartridge is the .270 Winchester Short Magnum (WSM) which utilizes the same head but a shorter, fatter case. A typical load for the .270 would be a 150 grain bullet propelled at 2,850 FPS giving approx. 2,700 foot pounds energy.

The .308 Winchester cartridge was introduced by Winchester in 1952. It was the commercial designation for the 7.62x51mm military round that Winchester were to release two years later. Until the introduction of the 5.56x45mm as the standard NATO round, the 7.62x51mm was the standard military rifle round in the UK and the USA; in the L1A1 SLR and the M14 rifle respectivley . It is still the standard machine gun round in both countries, in the M240 (previously the M60) in the US and the GPMG in the UK. It is an extremely common round worldwide and is used for both hunting and target shooting. If you join a shooting club in the UK, chances are most people will have .308 rifles. It typically propels a 168 grain bullet at 2,650 FPS giving 2,600 foot pounds energy.

The .303 British is one of the worlds legendary cartridges. It is the round that helped Britain win the first and second world wars. Developed in the 1880s as a black powder round, it converted to cordite in 1891 and then to smokeless propellant in 1910 with the mark 7 round. The .303 was first used in the Lee-Metford which replaced the Martini-Henry in 1888. This was soon superceded by the SMLE Mk.1 in 1904 and the SMLE Mk.3 in 1907. In 1939, the SMLE was replaced by the Lee-Enfield No.4 Mk.1 which was itself replaced by the No.4 Mk.2 shortly after the war. The Lee-Enfield No.4 Mk.2 remained the standard rifle of the British army until it was replaced by the 7.62x51mm L1A1 SLR towards the end of the 1950s. There are still hundreds of thousands of SMLEs and No.4s in use around the world, both as hunting and target rifles. They typically propel a 180 grain bullet at around 2,500 FPS giving 2,500 foot pounds energy.

The 6.5x55 Swedish Mauser was created by a Norwegian-Swedish committee in 1891 for use in new rifles both countries were considering at the time. The 6.5x55 Swede, as it tends to be called, is one of the most popular hunting calibres used in Europe due to it's combination of high power, moderate recoil and the extremely high BC of the heavy 6.5mm bullets. It is even fairly popular in America where national pride generally favours home grown calibres such as the .30-06 and .25-06. This is probably due to the number of military 6.5x55 rifles that ended up in America after WWII. As a calibre, 6.5x55 is showing something of a resurgence among UK stalkers and target shooters alike. Like all old military calibres, care must be taken when reloading this round. Modern rifles like mine can take far higher pressures and velocities than the older WWII rifles. A typical load for the 6.5x55 would be a 140 grain bullet propelled at 2,700 FPS giving approx. 2,300 foot pounds energy.

The .243 Winchester was introduced in 1955 by Winchester. Based on a .308 case necked down to 6mm, it quickly became a huge success. Since the 1963 Deer Act whch stipulated a minimum of .240 calibre with a minimum muzzle energy of 1,700 foot pounds, the .243 has become one of the standard UK deer rounds. Along with stalking use, it was used by the L.A.P.D. SWAT teams in their early days and, although not popular for target shooting in the UK, it makes an excellent 1,000 yard target round. It typically propels a 100 grain bullet at 3,000 FPS giving 2,000 foot pounds energy.

Developed in 2002 by Bill Alexander of Alexander Arms, the 6.5 Grendel was an evolution of Dr. Lou Palmisano's 6.5 PPC cartidge and was developed to provide a more powerful, longer range cartridge for the AR-15 platform. Using the same long, high BC 6.5mm bullets as the 6.5x55 Swede and many other benchrest cartridges, it extends the range of the AR-15's native .223 cartridge to allow the AR-15 to compete at upto 1,000 yards. It typical propels a 123 grain bullet at 2,650 FPS giving around 1,900 foot pounds energy.

The .22-250 started out in 1937 as a wildcat cartridge created by necking a .250 Savage case down to take a .224 bullet. There were originally several versions but the calibre was standardised (made 'factory') when Remington produced the 700 and 40XB target rifles in 1965. It is particularly popular as a varmint and pest control round in localities that suffer alot of wind, the small calibre and high speed help the bullet combat wind drift. In the UK, the .22-250 is extremely popular as a foxing round. It typically propels a 55 grain bullet at 3,800 FPS giving 1,750 foot pounds energy.

The .223 Remington was introduced in January 1964 just a month before it was adopted officially by the US military as the 5.56mm ball cartridge around which the Armalite AR-15, soon to be M16, was developed. The .223 is an extremely popular varmint round in the US and reasonably popular in the UK for foxing. The law in the UK has recently been changed to allow the use of .223 on Muntjac and Chinese Water deer but not on Roe which alot of the big shooting organistations wanted. Military surplus ('milsurp') ammo is cheap and available but due to the shorter, tighter neck of the .223 chamber, it is inadvisable to shoot 5.56mm ball ammo in a .223 due to excessive chamber pressures generated. There is a chamber design known as a 'Wylde chamber' that is sort of a cross between a .223 Rem and a 5.56x45mm chamber that allows the accurate shooting of both calibres. It typically propels a 55 grain bullet at 3,250 FPS giving 1,300 foot pounds energy.

Announced in 2004, the .204 Ruger was developed jointly between the gun maker Ruger and ammunition maker Hornady. It's big claim to fame is that it is the fastest commercially available 'factory' cartridge at 4,225 FPS. This velocity is not available to handloaders as Hornady use a proprietary propellant although just under 4,200 FPS is possible with standard propellants. The .204 Ruger is becoming a popular varmint round in both the USA and the UK (especially for foxes). Standard velocity for a 32 grain bullet is 4,225 FPS for just under 1,300 foot pounds energy.

The .17 Remington was introduced by Remington in 1971 for their 700 series of rifles. It is an excellent high velocity varmint round although it is heavily affected by wind as the tiny bullets have a poor ballistic coefficient. In still conditions, it is good for 2-300 yard shots on animals upto fox size. Typical velocity for a 25 grain bullet is 4,100 FPS giving nearly 1,000 foot pounds energy.



The .50 calibre Browning Machine Gun (or 12.7x99mm) is pretty much the king of all the 'standard' centrefires. It was conceptualised by John Browning during WWI as an anti-aircraft weapon and was based on a scaled-up .30-06 round. The new .50 cal heavy machine gun Browning created was designated the Browning 'M2'. The M2 was, and still is, used all over the world with airborne, armoured, ground and static troups. Nowadays, the .50 BMG is also available and widely used in bolt-action and semi-auto sniper and target rifles for military use and civilian target shooting, even in the UK. The velocity of a 700 grain bullet is around 3,000 FPS giving an amazing 14,000 foot pounds energy.

The .408 CheyTac (short for 'Cheyenne Tactical') was developed by Dr. John D. Taylor with the help of machinist William O. Wordman to fill the gap between the .338 Lapua Magnum and the .50BMG. It was designed to provide an anti-personnel, anti-sniper and anti-materiel round. All current .408 CheyTac ammunition is unusual in that it is made from a proprietary copper-nickel alloy rather than conventional copper-jacketed lead. The bullets are individually turned on Swiss-type CNC machines by Lost River Ballistic Technologies to ensure the tremendous accuracy needed. Due to the mono-metal construction and the unique turned design, the bullets have a tremendously high ballistic co-efficient of approximately 0.934 and the 419 grain projectile remains supersonic in flight to over 2,200 yards and even remains stable as it drops below the speed of sound. The .408 CheyTac typically fires a 419 grain projectile at 3,000 FPS giving an impressive 8,400 foot pounds energy.

The .338 Lapua Magnum (or 8.58x70mm)was created by Lapua of Finland in conjuction with Accuracy International of Great Britain as an anti-materiel and anti-personnel sniper round, although the .50BMG is more suitable for anti-materiel duties. The Iraq and Afghanistan conflicts have made it a combat proven round. As a hunting round, it is capable of taking any land animal in the world although some African countries specify .375 cal as a minimum. It must also be noted that this round is prohibited in countries that forbid private ownership of miltary calibres. The .338 Lap Mag typically fires a 250 grain bullet at 3,000 FPS giving a total energy of 4,900 foot pounds energy

The .375 Holland and Holland Magnum is arguably the classic hunting cartridge. It was introduced by Holland and Holland in Great Britain in 1912 and was originally called the .375 Belted Rimless Nitro-Express. With relatively light 235-270 grain bullets, it is a flat shooting round perfect for light to medium animals. Loaded with the heavier 300 grain bullets, it has the knock down power to deal with large, thick-skinned animals. In many regions with thick-skinned dangerous game animals the .375 H&H is seen as the sensible minimum acceptable calibre, and in many places it is now the legal minimum for hunting such game. African game guides, professional hunters and dangerous game cullers have repeatedly voted the .375 H&H as their clear preference for an all-round calibre. It typically fires a 250 grain bullet at 2,800 FPS giving 4,500 foot pounds energy.

The .338 Winchester Magnum was introduced by Winchester in 1958. It is based on the .458 Winchester Magnum and is suitable for all kinds of large game in North America ie Moose, Elk and Caribou. Interestingly, it is the most popular hunting calibre in Alaska where Polar and Grizzly bears can be encountered whilst hunting edible species. The only person I know who has a rifle in this calibre is Dave Ryan, the owner of Minsterley Ranges in Shropshire, who uses it for boar hunting. It typically fires a 250 grain bullet at 2,650 FPS giving 3,900 foot pounds energy.

The 6.5-284 has exploded on the international shooting scene in recent years. It is based on the .284 Remington, a round created to give 7mm bullet performance in a shorter action than the .30-06. The .284 Remington never really caught on however and the cases are now necked down to 6.5mm and used as the basis for a superb long-range target round. It is becoming increasingly popular and is starting to replace the .30 cal rounds as the long-range cartridge of choice. It typically fires a 142 grain bullet at 3,000 FPS giving 2,800 foot pounds energy.

The 7mm-08 is a direct copy of a wildcat cartridge developed around 1958 known as the 7mm-308. As the name suggests, it is simply a .308 Win case necked down to take the slightly higher BC 7mm bullet. The cartridge became the 7mm-08 and became 'factory' when Remington chambered their Model 700 and 708 for the round in 1980. The 7mm-08 is a useful hunting round as it fires bullets of a similar weight to the .308 and .30-06 but the smaller diameter 7mm bullets have a higher ballistic co-efficient so are flatter shooting and less affected by wind. It typically fires a 140 grain bullet at 2,800 FPS giving 2,400 foot pounds energy.

Previously known as the 6.5-08 A-Square, the .260 Remington was formalised by Remington in 1997 and is one of the many new calibres formed from .308 Winchester brass. Ballistically, with bullets upto a 140 grains, it is a similar cartridge to the 6.5x55mm Swedish Mauser although the 6.5 Swede can push heavier bullets to higher velocities. One advantage the .260 Remington has over the Swede is that it can be chambered in a shorter action. It typically fires a 140 grain bullet at 2,750 FPS giving 2,350 foot pounds energy.

The .243 Winchester Super Short Magnum is a fairly new rifle cartridge, introduced in 2003. It uses a shortened .300 Winchester Short Magnum case necked down to take a 6mm bullet. I have included it as an example of the trend for short, and super-short, magnums. The philosophy is that the shorter, fatter powder column burns more quickly and efficiently, giving less turbulence at the muzzle. The shorter actions required for this type of round can be shorter and stiffer than a longer action theoretically giving even more accuracy potential. The SM and SSM cartridges were initially very popular but they have turned out to be so called 'barrel burners' due to the faster, more intense burn and are still quite controversial among shooters. The .243 WSSM typically fires an 80 grain bullet at 3,500 FPS generating 2,200 foot pounds energy.

Although invented in the UK, the 6mm BR ('BR' simply stands for benchrest) has taken America by storm. 6PPC is perhaps more accurate to 300 yards but 6mmBR holds many records at 300- and 600 yards (and even some at 1000). The 6mm BR, also called 6mm Norma BR, was created by Norma who started with the 6mm Remington Benchrest case and made the neck longer and increased the base dimension slightly to give the 6mmBR we have today. It is accurate, easy to load for and is easy on barrels which makes it an extremely popular benchrest calibre. The 6mmBR typically fires a 105 grain bullet at 2,950 FPS giving 2,000 foot pounds energy.

I have included the .223AI as an example of 'Ackleyising'. Peter Ackley was a famous American wildcatter and gun nut who spent his life experimenting with guns and ammunition. Most cartridges can be Ackleyised. It involved cutting a chamber with much greater shoulder angle , usually combined with making the case walls more parallel. This has two benefits, firstly it increases the powder capacity of the case making it potentially 'faster' and the steeper shoulder angle lessens neck stretching when the round is fired. This reduces the need to trim the cases between firings. The cases for AI cartridges can be formed in two ways. The first method involves loading a small amount of fast pistol powder into the empty case topped with some inert filler like semolina or rice. When the round is fired, the blast and heat blows the brass into the shape of the AI chamber. The second method involves loading a lightish bullet and a mildish powder charge and firing the rifle. The .223 AI typically fires a 55 grain bullet at 3,600 FPS generating 1,600 foot pounds energy.

Developed in 1975 by Louis Palmisano and Ferris Pindell (the 'PPC' name stands for 'Palmisano and Pindell Cartridge'), the 6PPC is widely considered to be the most accurate rifle cartridge ever invented. There is something about the steep neck angle, nearly parallel case sides, small primer and flash hole and the ratio of the case diameter to the bore that seems be just right. Nobody is entirely sure why it is so amazingly accurate but the 6PPC absolutely dominates in 100, 200 and 300 yard benchrest competition shooting. 6mm bullets are widely available and the cases are easily made by necking down lapua .220 Russian brass cases. Sako of Finland make a factory round called 6PPC USA but these cartridges won't fit most tightly chambered benchrest rifles. The 6PPC typically fires a 62 grain bullet at 3,300 FPS giving 1,500 foot pounds energy.

The Soviet 7.62x39mm cartridge was designed during World War II and first used in the SKS carbine. Shortly after WWII, the AK-47 assault rifle was designed for the cartridge. The cartridge remained the standard Soviet cartridge until the 1970s and is still by far the most common intermediate rifle cartridge used around the world. It's successor, the 5.45x39mm cartridge is slightly less powerful but is more controllable in fully automatic fire due to the lower recoil. The change was in part a response to NATO switching from the 7.62x51mm cartridge to 5.56x45mm. The 7.62x39mm is not a particularly powerful round given the relatively small case volume and heavy, low BC bullet. The AK-47 is fairly popular in the UK when converted to straight-pull and is practical out to about 300 yards. The 7.62x39mm typically fires a 123 grain bullet at 2,300 FPS giving 1,500 foot pounds energy.

Invented in 1950 by Mike Walker of Remington, who also invented the famous Remington 700 rifle, the .222 was unusual in not being based on an existing cartridge but a totally fresh design. It's excellent inherent accuracy led to it being extremely popular for decades as a benchrest round and a varminting cartridge. The .222 was eventually succeeded in 1975 by the 6mm PPC, still a very popular benchrest cartridge, but although falling out of favour slightly, the .222 is still around. The .222 case provided the basis for the .223 Remington (which largely led to the .222 falling out of favour), the .221 Fireball and the new .204 Ruger. The .222 Remington typically fires a 55 grain bullet at 3,100 FPS generating 1,200 foot pounds energy.