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I posted a version of that "SFs want 6.8 Uppers" reply I posted here over on Glock Talk, very good thread. Somebody private mailed me, saying he has been working on the 6.8mm project for several years. His is what he posted on the Glock Talk "SFs Want 6.8mm" thread:

"The ideal military combat ammunition should provide both acceptable accuracy and adequate terminal performance out to at least 300 meters and preferably to about 600 meters. Ideal accuracy should be at least 1.5 MOA and preferably closer to 1 MOA. The bullet should penetrate at least 12 to 15 inches, with early yaw initiating within 1 or 2 inches of initial penetration. Fragmentation should occur at all ranges from zero to at least 300 meters. The bullet should be able to penetrate intermediate barriers such as automobile windshields, glass windows, building walls, and soft body armor. The ammunition should be light and compact enough for the soldier to carry an adequate supply of ammunition in magazines of at least a 25 round capacity. The rifle should be similar in size, weight, and ergonomics to the proven M4/M16 weapons. Recoil should be manageable to allow full auto fire when necessary, along with the more usual rapid, aimed semi-automatic fire. We can see from the above that .22 caliber rifle and carbine ammunition is probably too small for routine combat use, while .30 caliber ammunition is too large.

"The United States made two major missteps in its search for the ideal combat rifle caliber. In the late 1920’s, John Garand originally designed the M1 rifle in .276 caliber for which Frankford Arsenal provided the new ammunition that used a 125 gr bullet at approximately 2700 f/s. Ordnance trials determined that Garand’s .276 caliber T3E2 rifle was an ideal combat weapon, however, development of the .276 rifle was halted in 1932 because of the large remaining stocks of old .30-06 caliber M1906 150 gr FMJ ammunition left over from WWI and the U.S. military threw away an opportunity to adopt the superior performing .276 caliber 125 gr ammunition. Following WWII the United States military again made a colossal weapon system selection error when it rejected the British .280 caliber 140 gr bullet along with the T48/FAL rifle and instead selected the 7.62 x 51 mm cartridge and the T44/M14 rifle. In hindsight, we can hypothesize that a .280 (7 mm) FAL would probably have been an ideal combat rifle and would likely still be in use today had it been chosen. Continued ammunition development has confirmed the efficacy of these earlier attempts to develop ideal combat rifle ammunition and validated that the optimal combat rifle caliber is likely to be around .270 to .280 caliber.

"The SPC (Special Purpose Cartridge) program, has built on this historical data in developing the 6.8 x 43 mm SPC, which offers .277 caliber, 115 gr Match bullets fired at approximately 2650 f/s, yielding approximately 1 MOA accuracy and terminal performance significantly superior to that of all 5.56 mm ammunition currently available. Primary focus during cartridge design was on combat reliability, accuracy, flight characteristics out to 500 meters, and terminal performance. During load development, 6 mm, 6.5 mm, 7 mm, and 7.62 mm SPC variants were tested prior to selection of the best performing version -- the 6.8 mm SPC.

"Current accuracy, terminal ballistic, and operator testing indicates that the 6.8 x 43 mm SPC cartridge is extremely accurate and offers superior terminal performance and improved incapacitation capability from CQB to medium ranges (0 to 500 meters) as compared to ALL available 5.56 mm ammunition."