The 6mm Advanced Rifle Cartridge (6×38mm), or 6mm ARC for short, is a 6 mm (.243) caliber intermediate rifle cartridge introduced by Hornady in 2020, as a low-recoil, high-accuracy long-range cartridge, designed for use in the M16 platform at request of a specialized group within the U.S. DoD for its multipurpose combat rifle program.[4]
| 6mm Advanced Rifle Cartridge | ||||||||||||||||
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_.308_Win,_6mm_ARC,_300_AAC,_.223_Rem.jpg) Rifle cartridges (l. to r.) .308 Win, 6mm ARC, 300 AAC, .223 Rem | ||||||||||||||||
| Type | Centerfire rifle | |||||||||||||||
| Place of origin | United States | |||||||||||||||
| Production history | ||||||||||||||||
| Manufacturer | Hornady | |||||||||||||||
| Produced | 2020–present | |||||||||||||||
| Specifications | ||||||||||||||||
| Parent case | .220 Russian/6.5mm Grendel[1] | |||||||||||||||
| Case type | Rimless, bottleneck | |||||||||||||||
| Bullet diameter | 6.18 mm (0.243 in)[2] | |||||||||||||||
| Neck diameter | 6.96 mm (0.274 in)[2] | |||||||||||||||
| Shoulder diameter | 10.924 mm (0.4301 in)[2] | |||||||||||||||
| Base diameter | 11.201 mm (0.4410 in)[2] | |||||||||||||||
| Rim diameter | 11.20 mm (0.441 in)[3] | |||||||||||||||
| Rim thickness | 1.5 mm (0.059 in)[1] | |||||||||||||||
| Case length | 37.85 mm (1.490 in)[2] | |||||||||||||||
| Overall length | 57.40 mm (2.260 in)[2] | |||||||||||||||
| Case capacity | 2.20 cm3 (34.0 gr H2O)[citation needed] | |||||||||||||||
| Rifling twist | 190.5 mm (1:7.50 in) | |||||||||||||||
| Primer type | Small rifle | |||||||||||||||
| Maximum pressure (SAAMI) | 358.53 MPa (52,000 psi)[2] | |||||||||||||||
| Ballistic performance | ||||||||||||||||
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| Test barrel length: 610 mm (24 in) Source(s): [4] | ||||||||||||||||
Performance
editThe cartridge makes use of 6 mm (.243 in) 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. With the release in 2020, Hornady also launched three factory loads with 103, 105 and 108 gr (6.7, 6.8 and 7.0 g) bullet weights and advertised G1 ballistic coefficients of .512, .530 and .536 respectively.[5]
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 is almost comparable velocities and ballistic performance such as the .243 Winchester and 6mm Creedmoor, but out of a compact cartridge that 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,[6] 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, 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, 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.
SAAMI spec
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Compatibility with the AR-15
editFor an ordinary AR-15 rifle chambered for the .223 Rem/5.56mm NATO, a new barrel, magazine and bolt are required to convert to the 6mm ARC.[7] 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.[8] 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.
See also
editReferences
edit- ^ a b Hornady 6mm ARC Cartridge - What You Need to Know
- ^ a b c d e f g "Public Introduction - 6.5 Creedmoor - 6mm-ARC-Public-Introduction-Rev-2020-06-18.pdf" (PDF). Archived from the original (PDF) on 2020-10-01. Retrieved 2020-07-24.
- ^ SAAMI (2020): 6mm Advanced Rifle Cartridge [6mm ARC]. Retrieved 2023-01-16.
- ^ a b 6mm ARC - Hornady Manufacturing, Inc
- ^ Brand new rifle caliber: 6 mm ARC, Hornady's Advanced Rifle Cartridge! | all4shooters
- ^ Hornady 11th Edition Reloading Manual
- ^ Hornady's NEW 6mm ARC & Odin Work's Barrels - www.gunsamerica.com
- ^ gununiversity.com | 6mm ARC Released / Hands-On Testing and Comparisons, by Ryan Cleckner 3 June 2020