FWIW, Remington screwed the pooch in regards to the 6.8spc. They messed up the chamber drawings when they submitted it to SAAMI, and their ammo is anemic and notoriously inaccurate. Fortunately, DPMS and Model 1 Sales are the only manufacturers still clinging to the SAAMI chamber, all others have changed to either the SPC2 or the DMR chamber, and SSA and Hornady have stepped up in the ammo department.
Info on the 6.8 SPC:
http://demigodllc.com/articles/6.8-m...-arms-carbine/
http://www.dtic.mil/ndia/2008Intl/Roberts.pdf
http://www.yuntaa.com/FileManager/Do...4400144FB7B71E
http://68forums.com