6mm ARC vs .223 Rem: Cartridge Clash

Cartridge Clash: The 6mm ARC shows promise, but there's a tough road ahead if it seeks to dethrone the .223 Remington.

March 25, 2021 By Brad Fitzpatrick

In February 1964 the military adopted the 5.56mm Ball Cartridge M193, and the following month Remington introduced the civilian version—the .223 Rem.—to market. Based on the .222 Rem., the .223 Rem. was more than 100 fps faster than its parent cartridge. To be clear, the .223 Rem. and 5.56 NATO are similar but not identical rounds. I’ll stick with the .223 Rem. on this fight card, although virtually all of what can be said about the .223 Rem. applies to the 5.56 NATO.

Modern .223 Rem. factory loads range from 35 to 77 grains. Bullets in the 55- to 64-grain range remain popular for varmint hunting, target shooting and even big game hunting. The heavier .223 Rem. loads are mostly target loads designed to maximize ballistic coefficient for better ballistic performance.

Loaded with Hornady’s Frontier 55-grain hollowpoint Match bullet, a .223 Rem. rifle with a 24-inch barrel will reach a muzzle velocity of 3,240 fps and generate a muzzle energy of 1,282 ft.-lbs. That same load clings to just 311 ft.-lbs. of energy at 500 yards.

These numbers are obtained from a 24-inch barrel, and most hunting rifles and AR-15s won’t achieve those kinds of velocity and energy figures. But the .223 shoots relatively flat, produces next to no recoil and can be fired in a bolt gun or AR-15. While it has been popular for decades, the law enforcement and military communities complained it didn’t have enough energy to consistently neutralize threats.

Hornady’s newest cartridge is the 6mm ARC. ARC stands for Advanced Rifle Cartridge. The company’s goal was to provide better ballistics and terminal performance than the .223 while still fitting in an AR-15 rifle and still being manageable to shoot.

The parent cartridge is the 6.5 Grendel, which was developed in 2002 by Bill Alexander. The Grendel is a mild cartridge that performs well, but the Hornady engineers saw two areas for improvement. For starters, the Grendel is limited to bullets of about 129 grains. The longer, heavier, high BC bullets that have made the 6.5s famous are simply too long to fit in a Grendel. Hornady bumped back the Grendel’s shoulder and switched from a 6.5mm to a 6mm projectile. Those changes allowed the cartridge to use high BC bullets.

With a muzzle velocity of 2,750 fps from a 24-inch barrel, the ARC 108-grain ELD Match bullet generates 500 more foot-pounds of energy at the muzzle than a 75-grain .223 Match bullet. The 108-grain ELD match bullet has a BC of .536, substantially higher than the .223 Rem. 75-grain Match’s BC of .395.

The 6mm ARC also performs better in wind. In a 10-mph crosswind the 6mm ARC 108-grain bullet drifts 10.9 inches at 400 yards. The .223 75-grain bullet, by contrast, drifts more than 15 inches at that range, and the ARC’s advantage becomes more pronounced at longer ranges.

The .223 does have advantages, though. Because it’s been around longer there are many, many more factory loads currently available for the .223 than the 6mm ARC. Neither of these rounds produces a great deal of recoil, but the 6mm ARC’s recoil is more than that of the .223.

Whether you’re looking for an AR or a bolt gun, there are many more choices if you select the .223 Rem. The 6mm ARC is an AR-only proposition, and it requires Grendel magazines, which aren’t as widely available as .223/5.56 mags and hold fewer rounds.

The 6mm ARC shows promise, but there’s a tough road ahead if it seeks to dethrone the .223. For years shooters have been looking for the perfect AR round, something that offered a tangible advantage over the ballistics of the .223. The 6mm ARC does just that, but will this new round ever gain the footing required to shake the .223?