The 6 XC was developed to be an upgrade of the 6 mm Norma BR. The cartridges are first of all used in the 300 m discipline, but also up to 1000 yards in the US. In the development process, we noticed that its qualities are close to those of the 243 Win. Therefore we provide a factory load with 95 grain Nosler BST and 100 grain Norma Oryx. The 6 XC outshoots the 243 Win and is far more predictable.
One difference compared to the BR, is that we use a large primer and therefore avoid some problems. The case bottom has the same measurements as the BR/308 /243. Barrel twist is widely discussed, and the XC has the same twist as the BR, one in 8". This means that all bullets weighing 115 grains and less, will have twist enough to stabilize the bullets.
The XC barrel measurements are a little different to the BR. The lands are 6,00 mm compared to 6,02 mm for the BR and the groves are 6,20 instead of 6,18 mm. We basically scaled down a regular 6,5 barrel to 6 mm. The reason is to prevent barrel wear. You can use a regular 6 mm barrel for 6XC – we know a couple of target shooters who do, with a good result.