6mm ARC

The STANAG magazine-lenght 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 {{cvt|103|,|105|and|108|gr|g}} bullet weights and advertised G1 ballistic coefficients of .512, .530 and .536 respectively.[https://www.all4shooters.com/en/shooting/ammunition/hornady-6-mm-arc-new-ar-15-caliber-features/ Brand new rifle caliber: 6 mm ARC, Hornady's Advanced Rifle Cartridge! | all4shooters]

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.

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,[https://www.hornady.com/reloading/handbook Hornady 11th Edition 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-guns. Due to the lower MAP, the performance of 6mm ARC ammunition loaded to 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.[https://bobp.cip-bobp.org/uploads/tdcc/tab-i/6-mm-arc-en.pdf C.I.P. TDCC 6 mm Advanced Rifle Cartridge][https://www.vihtavuori.com/reloading-data-tool-rifle-handgun-cowboy-action-shooting/#/metrics/1/113/-1/-1/-1 Vihtavuori 6mm ARC reload data] According to the official C.I.P. rulings the 6mm ARC can handle up to {{convert|380.00|MPa|psi|abbr=on}} P_max 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 {{convert|475.00|MPa|psi|abbr=on}} PE piezo pressure.[https://bobp.cip-bobp.org/uploads/tdcc/tab-i/6-mm-arc-en.pdf C.I.P. TDCC 6 mm Advanced Rifle Cartridge] 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.{{Cite web |url=http://www.dstan.mod.uk/standards/defstans/05/101/01000100.pdf |title=Proof of Ordnance, Munitions, Armour and Explosives, Ministry of Defence Defence Standard 05-101 Part 1 |access-date=2011-07-16 |archive-url=https://web.archive.org/web/20110716024825/http://www.dstan.mod.uk/standards/defstans/05/101/01000100.pdf |archive-date=2011-07-16 |url-status=dead }}

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For an ordinary AR-15 rifle chambered for the .223 Remington/5.56mm NATO, a new barrel, magazine and bolt are required to convert to the 6mm ARC.[https://www.gunsamerica.com/digest/hornadys-new-6mm-arc-odin-works-barrels-first-field-tests/ Hornady's NEW 6mm ARC & Odin Work's Barrels - www.gunsamerica.com] The 6mm ARC utilizes the same bolt head size as the 6.5mm Grendel, and 6.5mm Grendel-compatible AR-pattern box magazines have also been used successfully with the 6mm ARC.[https://gununiversity.com/6mm-arc-review/ gununiversity.com | 6mm ARC Released / Hands-On Testing and Comparisons, by Ryan Cleckner 3 June 2020] The 6mm ARC therefore can also be a suitable chambering for shorter "mini-action" bolt-action rifles, such as the CZ 527 bolt action rifle mentioned previously.

Depending on their case material and bullet weight, dimensionally similar 6.5mm Grendel cartridges weigh {{convert|14.7|to|17.8|g|gr}}. That is significantly more when compared to {{convert|8|to|12|g|gr}} 5.56mm NATO rounds.

• .223 Remington
• 6mm AR
• 6 PPC
• 6.5mm Grendel

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{{Intermediate cartridges}}

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Category:Pistol and rifle cartridges