The
STANAG magazine-length cartridge was designed for and makes use of 6 mm (.243 in)
very-low-drag bullets, which are known for their high
ballistic coefficients due to the high
sectional density with less
drag and better
energy retention at extended ranges. This promotes greater terminal characteristics at longer distances without having to shift to a larger, heavier rifle platform than the AR-15. With the release in 2020, Hornady also launched three factory loads with bullet weights and advertised G1 ballistic coefficients of .512, .530 and .536 respectively. The 6mm ARC is a medium-power cartridge comparable to the
6.5mm Grendel, but with better ballistics thanks to the greater muzzle velocity achieved by using lighter 6 mm bullets and enough power to make use of the heavy 6 mm bullets. The 6mm ARC has almost comparable velocities and ballistic performance as the
.243 Winchester and
6.5mm Creedmoor, but out of a compact length cartridge that, without having to deal with substantial
bolt thrust or breech pressure increase related drawbacks, has less recoil and fits into the standard
AR-15 length actions. The ability to use a cartridge with this level of performance in an AR-15 platform and especially with high BC bullets within the constraint of magazine length limitations, make this cartridge an excellent choice for use in an AR-15.
SAAMI, C.I.P. and commercial data In addition to the above comments, there is some confusion regarding the 6 mm ARC's performance. This is because loading data given in some manuals such as the
11th Edition Hornady Reloading Manual, for example, has two sets of data. The first set of data is loaded to the
SAAMI maximum average pressure (MAP) of 52,000 psi (358.53 MPa), which is stated to be suitable for gas-operated firearms such as the AR-15 platform and its derivatives. The second set of data is loaded to a MAP of 62,000 psi (428.48 MPa), which is stated to be for use with
bolt action guns such as the
CZ 527. The Hornady manual states that this second set of data should not be used in gas-operated firearms. Due to the lower MAP, the performance of 6mm ARC ammunition loaded to 10,000 psi lower gas-gun pressures will, on average, be less than firearms loaded to bolt action pressures when using the same barrel length. When using shorter barrels, which are common on gas-guns, the difference will be even more pronounced. For example, the data in the Hornady 11th Edition Manual for an 18 in (457 mm)-barrelled AR-15 platform firearm was on average 200–300 ft/s (60–90 m/s) less than the data for the 24 in (610 mm)-barrelled CZ 527 bolt action rifle. Reloading data publications from and commercially offered ammunition in
C.I.P. member states must comply with C.I.P. procedures, rulings and legislation. According to the official
C.I.P. rulings the 6mm ARC can handle up to Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be
proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. This means that 6mm ARC chambered arms in C.I.P. regulated countries are currently (2025) proof tested at PE piezo pressure. For small arms ammunition for use in "
non-NATO Chamber" weapons,
NATO has chosen to conform to the procedures as defined by the current C.I.P. legislation. == Compatibility with the AR-15 ==