6 mm B.R. Rem.

The 6mm BR Remington, also known as the 6mm Bench Rest Remington, is a centerfire cartridge designed specifically for benchrest shooting. It was introduced by Remington Arms Company in the early 1960s, and is based on a necked-down version of the .308 Winchester case.

The cartridge has a bullet diameter of .243 inches (6.17mm) and a case length of 1.56 inches (39.6mm). It is known for its high accuracy and low recoil, and is capable of producing consistent, sub-MOA (minute of angle) groups at ranges up to 600 yards.

The 6mm BR Remington is commonly used for benchrest competition shooting, where precision and accuracy are the top priorities. It is also used for varmint hunting, thanks to its flat trajectory and high velocity, which make it capable of delivering accurate shots at longer ranges.

The cartridge is typically loaded with bullets weighing between 65 and 105 grains, with the most popular bullet weights being in the 80 to 90 grain range. These lightweight bullets allow for higher velocities, which translates into flatter trajectories and less wind drift.