6x45 mm
Encyclopedia
The 6×45mm is a rimless, bottlenecked cartridge
based on the .223 Remington
or 5.56 NATO cartridge necked up to .243 (6mm). The cartridge is also known as the 6mm-223 Remington or 6mm/223.
which already had a loyal following in benchrest shooting
fraternity. Benchrest shooters soon took notice of the cartridge and began building custom rifles chambered for the cartridge. As a testament to the 6×45mm’s accuracy, Jim Stekl, who at that time managed Remington’s custom shop and developer of the .22 BR cartridge, scored an aggregate record of 0.3069 inches (7.8 mm) in the 1973 IBS 200 yard Sporter category. However, its use in competitive shooting waned with the arrival of the 6mm BR and 6mm PPC cartridges on the benchrest shooting scene.
The advantage of the 6×45mm over the .223 Remington is that it is capable of being loaded with heavier bullets with better ballistic coefficient
ratings than its parent cartridge, the .223 Remington. This results in a flatter trajectory, less susceptible to wind drift and with better energy retention characteristics.
The cartridge is extremely efficient with its small powder
charge. This translated to excellent barrel life. The cartridge has a very low recoil and muzzle blast which make it a pleasant cartridge to shoot.
Since the cartridge was never commercially adopted by an ammunition manufacturer, it has remained a wildcat cartridge
since it inception. However, making cases from existing .223 Remington brass is as simple as running the case through a 6×45mm die
. The availability of .223 cases, the ease of forming, and the light power charge make for a very affordable shooting cartridge.
The cartridge maximum overall length is nominally given as 2.23 inches (5.7 cm), however, as the cartridge is a wildcat cartridge chamber dimensions may vary from manufacturer to manufacturer. For this reason overall length of the cartridge may vary.
The cartridge gained a following in South Africa where it was used to hunt small antelope and gazelle species such as duiker, impala, klipspringer, springbok and the Thompson’s gazelles. In North America it is capable of taking small predator species such as bobcats, coyotes and foxes. In Europe, it can be used for small goat and deer species such as the roe deer and chamois where legally permitted.
An improved version of the cartridge called the 6mm TCU was developed for metallic silhouette shooting. While the cartridges are quite similar they are not interchangeable.
/M-16
can easily be converted to the 6×45mm with a simple barrel swap with little or no further modifications to the rifle. This is also true for rifles such as Ruger’s Mini 14 and most bolt action rifles chambered for the .223 Remington cartridge. The 6×45mm cartridge provides better down range performance than the .223 Remington or the 5.56 NATO cartridges. The cartridge had been offered by Cooper Arms
, Kimber
and a few other rifle manufacturers in their rifles as a regular factory chambering for a period of time.
However, the cartridge’s break through was in the area of handgun hunting where it became very popular. The bolt action Remington XP-100 pistol and the break-open Thompson/Center Contender
handgun were chambered for the cartridge. It provided a flat shooting cartridge capable of taking small deer
and small game species.
Cartridge (firearms)
A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...
based on the .223 Remington
.223 Remington
The .223 Remington is a sporting cartridge with almost the same external dimensions as the 5.56×45mm NATO military cartridge. The name is commonly pronounced either two-two-three or two-twenty-three. It is loaded with a diameter, jacketed bullet, with weights ranging from , though the most common...
or 5.56 NATO cartridge necked up to .243 (6mm). The cartridge is also known as the 6mm-223 Remington or 6mm/223.
History
Soon after the release of the .223 Remington as a commercial cartridge, shooters began experimenting with the cartridge in an attempt to improve its performance. Several of these experimenters necked up the .223 Remington to 6mm as the .24 (6.1 mm) caliber bullets provided better external ballistic performance over .22 (5.7 mm) caliber bullets. While several variation existed between early versions of these cartridges, the 6×45mm as we know it today became the standard version of the cartridge which is simply a necked up version of the .223 Remington without any further modifications or improvements made to it.General Information
The cartridge’s inherent accuracy was a carry over from the .222 Remington.222 Remington
The .222 Remington aka the Triple Deuce/Triple Two/Treble Two is a centerfire rifle cartridge introduced in 1950, and was the first commercial rimless .22 cartridge made in the United States...
which already had a loyal following in benchrest shooting
Benchrest shooting
Benchrest shooting is a sport in which very accurate and precise rifles are shot at paper targets from a rest or bench from a sitting position. Benchrest shooters are notoriously detail-oriented and constantly trying to further the accuracy potential of the rifle through experimentation. Nearly...
fraternity. Benchrest shooters soon took notice of the cartridge and began building custom rifles chambered for the cartridge. As a testament to the 6×45mm’s accuracy, Jim Stekl, who at that time managed Remington’s custom shop and developer of the .22 BR cartridge, scored an aggregate record of 0.3069 inches (7.8 mm) in the 1973 IBS 200 yard Sporter category. However, its use in competitive shooting waned with the arrival of the 6mm BR and 6mm PPC cartridges on the benchrest shooting scene.
The advantage of the 6×45mm over the .223 Remington is that it is capable of being loaded with heavier bullets with better ballistic coefficient
Ballistic coefficient
In ballistics, the ballistic coefficient of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration—a high number indicates a low negative acceleration. BC is a function of mass, diameter, and drag coefficient...
ratings than its parent cartridge, the .223 Remington. This results in a flatter trajectory, less susceptible to wind drift and with better energy retention characteristics.
The cartridge is extremely efficient with its small powder
Smokeless powder
Smokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...
charge. This translated to excellent barrel life. The cartridge has a very low recoil and muzzle blast which make it a pleasant cartridge to shoot.
Since the cartridge was never commercially adopted by an ammunition manufacturer, it has remained a wildcat cartridge
Wildcat cartridge
A wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and firearms are not mass produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge.Developing and using wildcat cartridges does not...
since it inception. However, making cases from existing .223 Remington brass is as simple as running the case through a 6×45mm die
Handloading
Handloading or reloading is the process of loading firearm cartridges or shotgun shells by assembling the individual components , rather than purchasing completely assembled, factory-loaded cartridges...
. The availability of .223 cases, the ease of forming, and the light power charge make for a very affordable shooting cartridge.
Performance
The advantage of the 6×45 mm over the .223 Remington is that it is capable of being loaded with heavier bullets with better ballistic coefficient ratings than its parent cartridge, the .223 Remington. This results in a flatter trajectory (with bullets of similar weight), less susceptibility to wind drift and better energy retention characteristics.| Cartridge | Criteria | Muzzle | 50 yd (45.7 m) | 100 yd (91.4 m) | 150 yd (137.2 m) | 200 yd (182.9 m) | 300 yd (274.3 m) |
| .223 Remington 55 gr Sierra FMJ-BT | Velocity | 3300 ft/s (1,005.8 m/s) | 3110 ft/s (947.9 m/s) | 2929 ft/s (892.8 m/s) | 2754 ft/s (839.4 m/s) | 2587 ft/s (788.5 m/s) | 2269 ft/s (691.6 m/s) |
| Energy | 1330 ft·lbf (1,803.2 J) | 1181 ft·lbf (1,601.2 J) | 1047 ft·lbf (1,419.5 J) | 926 ft·lbf (1,255.5 J) | 817 ft·lbf (1,107.7 J) | 629 ft·lbf (852.8 J) | |
| 6×45mm 90 gr Sierra FMJ-BT | Velocity | 2700 ft/s (823 m/s) | 2580 ft/s (786.4 m/s) | 2462 ft/s (750.4 m/s) | 2348 ft/s (715.7 m/s) | 2237 ft/s (681.8 m/s) | 2023 ft/s (616.6 m/s) |
| Energy | 1457 ft·lbf (1,975.4 J) | 1330 ft·lbf (1,803.2 J) | 1212 ft·lbf (1,643.3 J) | 1102 ft·lbf (1,494.1 J) | 1000 ft·lbf (1,355.8 J) | 818 ft·lbf (1,109.1 J) | |
| Values courtesy of the Hornady Ballistic Calculator | |||||||
Cartridge Specifications
The 6×45 mm is a wildcat cartridge and has not been standardized by any agency nor has it been offered a a proprietary cartridge by any ammunition manufacturer. Some specialty rifle makers such as those that sell varmint rifles offer rifles chambered in this cartridge. Specifications for the cartridge are derived from the necked up parent cartridge without further improvement.The cartridge maximum overall length is nominally given as 2.23 inches (5.7 cm), however, as the cartridge is a wildcat cartridge chamber dimensions may vary from manufacturer to manufacturer. For this reason overall length of the cartridge may vary.
Hunting Applications
Many countries and many U.S. states require a minimum of .24 caliber (6.1 mm) for hunting certain game species, such as deer. In such countries and states the 6×45mm would be legal for hunting as long as no further requirement regarding power, energy, or case length is stipulated. However, it should be considered a marginal cartridge for these game species at best.The cartridge gained a following in South Africa where it was used to hunt small antelope and gazelle species such as duiker, impala, klipspringer, springbok and the Thompson’s gazelles. In North America it is capable of taking small predator species such as bobcats, coyotes and foxes. In Europe, it can be used for small goat and deer species such as the roe deer and chamois where legally permitted.
An improved version of the cartridge called the 6mm TCU was developed for metallic silhouette shooting. While the cartridges are quite similar they are not interchangeable.
Platform Availability
The AR-15AR-15
The AR-15 is a lightweight, 5.56 mm, air-cooled, gas-operated, magazine-fed semi-automatic rifle, with a rotating-lock bolt, actuated by direct impingement gas operation. It is manufactured with the extensive use of aluminum alloys and synthetic materials....
/M-16
M16 rifle
The M16 is the United States military designation for the AR-15 rifle adapted for both semi-automatic and full-automatic fire. Colt purchased the rights to the AR-15 from ArmaLite, and currently uses that designation only for semi-automatic versions of the rifle. The M16 fires the 5.56×45mm NATO...
can easily be converted to the 6×45mm with a simple barrel swap with little or no further modifications to the rifle. This is also true for rifles such as Ruger’s Mini 14 and most bolt action rifles chambered for the .223 Remington cartridge. The 6×45mm cartridge provides better down range performance than the .223 Remington or the 5.56 NATO cartridges. The cartridge had been offered by Cooper Arms
Cooper Firearms of Montana
Cooper Firearms of Montana was founded in 1990 by Dan Cooper and two other former Kimber of Oregon employees.-History:Cooper was created to build affordable custom-quality accurate rifles. As they put it "Rifles should shoot as well as they look and vice versa". All Cooper rifles carry an accuracy...
, Kimber
Kimber Manufacturing
Kimber Manufacturing is an American company that designs, manufactures, and distributes small arms such as M1911 pistols, Solo pistols and rifles. The USA Shooting Team, Marines assigned to Special Operations Command, and the LAPD SWAT team use Kimber pistols....
and a few other rifle manufacturers in their rifles as a regular factory chambering for a period of time.
However, the cartridge’s break through was in the area of handgun hunting where it became very popular. The bolt action Remington XP-100 pistol and the break-open Thompson/Center Contender
Thompson Center Arms
Thompson/Center Arms Company is an American firearms company based in Rochester, New Hampshire. The company is best known for its line of interchangeable barrel single-shot pistols and rifles. Thompson Center manufactures muzzleloading rifles and is credited with creating the resurgence of their...
handgun were chambered for the cartridge. It provided a flat shooting cartridge capable of taking small deer
Deer hunting
Deer hunting is survival hunting or sport hunting, harvesting deer, dating back to tens of thousands of years ago. Which occurred though out Europe Asia and North America There are numerous types of deer throughout the world that are hunted.- New Zealand :...
and small game species.