6mm BR

Soon after the introduction of the .308 Winchester-based wildcat .308×1.5" Barnes cartridge, wildcatters and experimenters began developing their own wildcats based on .308 Winchester. By 1963 there were several .22 (5.56 mm) and .24 (6 mm) caliber cartridges based on the Barnes’ cartridge. The new cartridges’ accuracy and efficiency was noticed by the bench rest shooting community. The .24 caliber (6 mm) cartridge version became known as the 6mm Bench Rest or the 6mm BR due to its widespread use in the sport of bench rest shooting. Because the cartridge was a wildcat and was not standardized until several years later, several variations of the cartridge existed. Cases required fire forming in the chamber as chambers of the rifles varied from one to another. Several 6mm BR variants exist apart from the Remington and Norma versions: the 6mm BRX, 6mm Dasher, 6 mm BRBS 6 mm UBL and 6mm BR Farè. These wildcats cartridges require reshaping factory cartridge cases and handloading. Over time, some wildcats became standardized and officially listed by the C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) and commercially available as factory produced brass for handloaders. 6mm BR Remington In 1978 Remington started manufacturing their Remington 40-X rifle in the 6mm BR and named their version of the cartridge the 6mm Bench Rest Remington. By 1988 Remington was also manufacturing ammunition. Remington continues to offer the 6mm BR Remington in the 40-X series rifles. The Remington version of this cartridge is now considered to be obsolete. However, the chamber of the Norma version provided a longer throat making allowances for the seating of very low drag (VLD) bullets. The 6mm BR Norma has become a popular chambering in match rifles used in ISSF and CISM and other 300 metres rifle disciplines. C.I.P listed and ruled variants In 2025 the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings contained four 6mm BR chambering variants. • 6mm BR Remington (1994) • 6mm BR Norma (1995) • 6mm BR Farè (2015) • 6mm Dasher (2023) Becoming listed by the C.I.P. ends the wildcat status of a cartridge by law in C.I.P. member states. ==6mm BR Remington cartridge dimensions==

The 6mm BR Remington cartridge is a .308×1.5" Barnes cartridge necked down to accommodate .243 bullets. The .308×1.5" Barnes cartridge is based on the .308 Winchester case shortened to . It is one of the earlier cartridges to follow the short, fat design concept. Short fat cartridges have characteristics that make them more efficient and accurate. : 6mm BR Remington maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm). Americans would define the shoulder angle at alpha/2 = 30 degrees. The common rifling twist rate for this cartridge is 228.600 mm (1 in 9 in), 6 grooves, diameter of lands = , diameter of grooves = , land width = and the primer type is large rifle. According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 6mm BR Remington case can handle up to Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. ==6mm BR Norma cartridge dimensions==

The 6mm BR Norma cartridge was introduced by Norma in 1996. It is based on the 6mm BR Remington cartridge, although where Remington's cartridge was intended for bullets of about , Norma standardized their set of chambering specifications for a very low drag (VLD) bullet of over , thus realizing the long-range capabilities of the cartridge. This required a much longer throat in rifles chambered for the Norma cartridge. : 6mm BR Norma maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm). Americans would define the shoulder angle at alpha/2 = 30 degrees. The common rifling twist rate for this cartridge is 203.20 mm (1 in 8 in), 6 grooves, diameter of lands = , diameter of grooves = , land width = and the primer type is large rifle. According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 6mm Norma BR case can handle up to Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. ==6mm Dasher==

In 2023 the 6mm Dasher became listed by the C.I.P. which ended its wildcat status. The 6mm BR Norma functioned as the parent cartridge for the 6mm Dasher cartridge. Featuring a 40-degree Ackley-type shoulder and about 5 to 10 percent more case capacity over the parent case for obtaining higher muzzle velocities to improve long-range capabilities combined with a barrel common rifling twist rate suited for very low drag (VLD) bullets of over . It is primarily used by competition shooters for precision shooting disciplines. The 6mm Dasher has been used to set records in the benchrest community, and has also become popular among competitors in the Precision Rifle Series (PRS) community. Factory produced 6mm Dasher cartridge cases are commercially available for handloading. Americans would define the shoulder angle alpha/2 = 40 degrees. The common rifling twist rate for this cartridge is 196.85 mm (1 in 7.75 in), 6 grooves, diameter of lands = , diameter of grooves = , land width = and the primer type is small rifle. According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 6mm Dasher case can handle up to Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. ==6mm BR Farè==

In 2015 the 6mm BR Farè became listed by the C.I.P. which ended its wildcat status. The 6mm BR Farè cartridge originates from Italy and is a high pressure variant, as its Pmax piezo pressure is rated over the other C.I.P. listed 6mm BR variants. Factory produced 6mm BR Farè cartridge cases are currently (2025) not commercially available. Americans would define the shoulder angle alpha/2 ≈ 40.12 degrees. The common rifling twist rate for this cartridge is 203.20 mm (1 in 8 in), 6 grooves, diameter of lands = , diameter of grooves = , land width = and the primer type is large rifle. According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 6mm BR Farè case can handle up to Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. ==See also==