The 6mm BR with a 40-degree Ackley shoulder, gaining slightly more case capacity and more consistent fire-forming than the parent 6mm BR. A benchrest staple that directly informed the development of the 6mm Dasher. Revered for sub-MOA consistency at 600 yards.
Type: Rifle
Introduced: 1978, United States
Parent case: 6mm BR Norma
Standardization: Wildcat
Bullet diameter: 0.243" (6.17 mm)
Max pressure: 55,000 PSI
Rim type: Rimless
Primer: Small Rifle
Typical twist rate: 1:7.5
Muzzle velocity: 2900–3150 fps
Muzzle energy: 1625–2380 ft-lbs
Effective range: 400 yd
Common bullet weights: 87, 95, 103, 105, 107, 108 gr
Primary use: target, competition
Production status: Active
Also known as: 6mm BRA · 6mm BR Ackley Improved · 6BR Ackley · 6 BR Ackley
History: As the 6mm BR Norma gained traction in F-Class and benchrest competition, shooters began fire-forming the brass to an improved shoulder for marginally better performance and brass life. The 6 BRA became a well-established benchrest cartridge in its own right and is recognized as the developmental ancestor of the 6mm Dasher.