The 6.8 SPC was designed to address the deficiencies of the terminal ballistics of the 5.56×45mm NATO cartridge currently in service with the armed forces of all NATO-aligned countries.

The 6.8 SPC (6.8×43mm) was initially developed by Master Sergeant Steve Holland and Chris Murray, a United States Army Marksmanship Unit gunsmith,[9] to offer superior downrange lethality over the 5.56 NATO/.223 Remington in an M16-pattern service rifle with minimal loss of magazine capacity and a negligible increase in recoil.

[11] In tests comparing various caliber bullets using a .30 Remington parent case, Holland and Murray determined that a 6.5 mm caliber projectile had the best accuracy and penetration, with historical data going back for decades of US Army exterior and terminal ballistic testing, but a 7 mm projectile had the best terminal performance.

The 6.8mm SPC is not the ballistic equal of the 7.62×51mm NATO cartridge, but it has less recoil, has been said to be more controllable in rapid fire, and is lighter, allowing operators to carry more ammunition than would otherwise be possible with the larger caliber round.

In recent developments (the period 2008–2012) the performance of the 6.8 SPC has been increased by approximately 61 to 91 m/s (200 to 300 ft/s) by the work of ammunition manufacturer Silver State Armory LLC (SSA) and a few custom rifle builders using and designing the correct chamber and barrel specifications.

[20] In 2007, both the U.S. SOCOM and the U.S. Marine Corps decided not to field weapons chambered in 6.8 mm due to logistical and cost issues.

Dedicated AR upper receiver assemblies chambered for the round are produced by a number of smaller firms, including Daniel Defense.

[23] The Stag Arms hunter and tactical models utilize the newer chamber (SPC II) and specified twist rates to accommodate higher pressure loadings, as well as upper receivers in left-handed configurations.