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The .280 Ackley Improved (.280 AI) was the result of the .280 Remington case modification by P.O Ackley, who pushed out the sidewalls at the shoulder to near parallel and steepened the shoulder angle to 40 degrees in order to increase powder capacity, thus along with increasing the allowable pressure, resulted in increasing the bullet initial velocity by approximately 100 fps.
The 6.8mm Remington Special Purpose Cartridge (6.8 SPC, 6.8 SPC II or 6.8×43mm) is a rimless bottlenecked intermediate rifle cartridge that was developed by Remington Arms in collaboration with members of the U.S. Army Marksmanship Unit and United States Special Operations Command [6] to possibly replace the 5.56 NATO cartridge in short barreled rifles (SBR) and carbines.
Since cases for the .280 RCBS could be formed by firing .280 Remington ammo in a rifle chambered for the former, Ackley abandoned the 7mm-06 Improved and started chambering rifles for the .280 RCBS. He then changed the 35-degree shoulder to 40-degrees and the .280 Ackley wildcat was born.
.17 Ackley Bee.17 CCM.17 Hornet.17 Mach IV.17 Remington.17 Remington Fireball.19-223.19 Badger.19 Calhoon Hornet.20 BR.20 Tactical.20 VarTarg.204 Ruger.22 Accelerator.22 Hornet.22 CHeetah.218 Bee.219 Donaldson Wasp.219 Zipper.303/22.22 Savage Hi-Power.22 BR Remington.22 Eargesplitten Loudenboomer.22 PPC.22 Remington Jet.22 Spitfire.22 WCF
Ackley's loads only managed 4,600 ft/s (1,400 m/s)(Mach 4.2), firing a 50-grain (3.2 g) bullet. Based on a .378 Weatherby Magnum case, the case is impractically over-capacity for the bore diameter, and so the cartridge remains a curiosity. The advent of new slower-burning smokeless powders may have changed the equation. [8]
The .260 Remington, loaded with very low drag bullets such as the 138 gr (8.9 g) Lapua, 140 gr (9.1 g) Berger, or 142 gr (9.2 g) Sierra, can match the 1,000 yd (910 m) performance of the 190 gr (12 g) Sierra-loaded .300 Winchester Magnum, with better resistance to wind deflection and half the recoil. [12]
The GEC evolved from the Center for Strategic Counterterrorism Communications, established by the Obama administration in 2011 to counter online extremist recruitment and propaganda.
This variant uses an Ackley Improved fire formed case with less tapering and a 40-degree higher shoulder permitting a larger powder capacity. It is claimed by its maker to be capable of driving a 6.5 g (100 gr) or heavier grain projectile at 880 m/s (2,900 ft/s) (satisfying the "6mm Optimum"). [citation needed]