6mm PPC --> 6.5 Grendel --> 6mm ARC - Why?

[LRRPF52]

6mm PPC typically has much looser rifling (1-14” twist), but the cases are closer to each other than pretty much any other 2 cases in history that I can think of.

PPC has typically been loaded with short, lightweight bullets. Some early AR-15 Hi-Power shooters started taking Colt 7.62x39 Bolts and magazines and having custom 6mm PPC rifles built with tighter twist back in the 1990s. I remember at least one article in a gun rag about it, showing the unique modifications and thinking it was far out there, but it nestled in the back of my mind when considering a DM/Light Sniper concept. I had zero interest in tube guns for competitions at the time, and only cared about how developments might affect military applications.

The main minute differences between 6mm PPC and 6mm ARC are neck length and shoulder location. ARC’s shoulder is slightly more forward, and PPC’s neck is longer. Both have the same case rim diameter and web, and 30 degree shoulders.

6mm PPC case length is a tiny bit longer (1.503” PPC vs 1.490” for the ARC).

Neck diameters are also different:

6mm PPC Match: .262”
6mm PPC USA SAKO: .269"
6mm ARC: .274”






I suspect Bench Rest shooters are going to get upset as they see Lapua 6mm PPC brass take the brunt of orders that were previously being filled with Grendel brass, if the demand is big enough for 6mm ARC. Too easy to fire form with long loads fed from lead sleds.