If a new cartridge could service the U.S.’s elite combat units, great, but if Hornady could simply push the envelope again for glory, country and profit, shouldn’t it? This is the private industry’s strength and what makes America great. Besides, there are plenty of hunters who love the AR-15 in both 5.56 NATO and .300 Blackout, but plenty also realize that it’s marginal at best for larger deer and hogs, especially beyond 100 yds.
The Answer: 6mm Advanced Rifle Cartridge
After much R&D, Hornady’s engineers and staff produced the 6mm ARC (Advanced Rifle Cartridge), a short, fat, PPC-looking round that’s very deceiving for the power that it actually contains. In a nutshell, Hornady took a 6.5 Grendel case, necked it down to 0.243″ (6 mm) diameter and moved the 30-degree shoulder back 0.030″ so the company’s long ELD bullets could be seated shallowly yet with its overall length still under 2.260″. The company optimized (blended) powders for it and experimented with charges and bullet weights until engineers approved. From an 24″ test barrel, the 6mm ARC launched a 108-gr. ELD Match bullet at 2800 f.p.s. for 1,880 ft.-lbs. of energy at the muzzle.
But now that you know about the 6mm ARC, you might be thinking, doesn’t the 6.5 Grendel with its heavier bullet but lower velocity accomplish the same thing from an AR-15? Is Hornady splitting hairs? Is this a marketing ploy?
“Absolutely not,” said Hornady ballistician Jayden Quinlan, who conceptualized the ARC. “The farther out your target is, the more advantage you’ll see. For the guy who’s shooting at 200 to 300 yards, he has the advantage of a bigger bullet selection over the Grendel. For the guy shooting beyond 300, there’s a distinct advantage in hit probability and wind deflection.”
Fact is, plenty of carbine gurus opine that the Grendel fell short in the category of long-range effectiveness, mainly because the long 6.5mm bullets consumed too much powder capacity of the little PPC-based case, and the round, therefore, does not quite have the horsepower (2475 f.p.s. from an 18″ barrel) it needs for its 123-gr. ELD bullet to be effective much past 800 yds. (370 ft.-lbs. at 1,000 yds.). To become more efficient, the bullet would need to be longer and heavier, but the Grendel is at the end of its rope because longer bullets would have to be seated further into the case, robbing propellant space. Furthermore, ballisticians have learned that the deeper a bullet is seated into a case the greater the probability of it wobbling in flight, degrading accuracy, and that’s why, unlike the Grendel, the PRC’s and ARC’s bullets are seated so shallowly.