European Sporting Cartridge
6mm Norma BR ( 6mm Norma Bench Rest )
Although these cartridges share the same case dimensions they are considered different calibers
due to the different standardized projectile weights.
Remington introduced the "6mm BR Remington or 6mm Bench Rest Remington" in 1988, but the design goes
back to the early 1960s as wildcats designed by shortening the  308 and reducing the mouth to accept 6mm
Remington designed this cartridge as a bench rest cartridge with a 70 grain projectile.
(The 6mm BR Remington is now obsolete, no longer factory produced by Remington)
Norma introduced the "6mm Norma BR or 6mm Norma Bench Rest" in 1996, considering it a long  range
cartridge  using a design with a 100 grain (very low drag) or (VLD).
(The 6mm Norma BR is consider a current cartridge, still produced, but hard to find.)
As Norma is based in Europe, they had to introduce the "6mm Norma BR" as a completely  different caliber,
or new cartridge due to the fact they standardized it with a 100 grain projectile vs. the 70 grain "
6mm BR Remington cartridge".  Also different OAL. (Over all length)
In other words, they have different standard projectile weights so are considered different calibers.
Confused? I know sometimes it doesn't make sense.
$ 3.75 per Cartridge
$4.75 per Cartridge
6mm BR Remington
6mm Bench Rest
This was factory
made by Remington
and is now currently
American Obsolete Sporting Cartridge
6mm BR Remington( 6mm Bench Rest Remington)
6mm Norma BR
Bench Rest
by Lapua
105 grain
Jacketed Hollow Point
Boat-Tail projectile