Reid Hendrix of Tactical Response rips the 6.8 SPC as an over-priced, hard-to-find cartridge that needs expensive, specialized magazines. He compares it to standard 7.62×39… and makes a pretty good case for the old “.30 Russian” being the better cartridge due to economy and ubiquity, even if the 6.8 has slight performance advantages.
He makes valid points. The 6.8 SPC was designed for a very narrow performance profile as a “bridge” between the 5.56 NATO and 7.62 NATO that would work in the short barrel of an M4 carbine.
It performed okay, but was never a superstar. It has simply never performed well enough to earn its keep as a commercial rifle cartridge.
As of right now, 7.62×39 ammo can be had from many vendors starting at 23¢ a round, while 6.8 SPC is running at 90¢ a round and up. Considering “close enough” ballistics and huge economic advantage of the 7.62×39, I think he’s making a solid call, and perhaps one that could apply to the 300 BLK just as easily.