The .450 Bushmaster is a rimless case that started as the .284 Winchester cut down to 1.7 inches, then opened up to accept a .452 bullet. The .450 Bushmaster cartridge was first designed by LeMag Firearms and then licensed to Bushmaster. Knowing that the success of any new cartridge hinges on readily available ammunition, Bushmaster went to Hornady for factory-loaded ammo.
At that time, Hornady was having great luck with its 240-grain .452 SST Flextip bullet in muzzleloaders, and thought that bullet would be a great match for the .450 Bushmaster cartridge. That was the primary load in the .450 Bushmaster for years, and it stayed that way until Remington and Bushmaster became sister companies. Now, the .450 Bushmaster loaded with the Remington 250-grain CoreLokt SP or the radical 260-grain AccuTip will drive an expanding bullet at about 2,200 fps from a 20-inch barrel. Sighted-in about two inches high at 100 yards, the .450 Bushmaster is only six inches low at 200 yards. For the deep-woods or open-country hunter, this round does anything the .45-70 does, in a much shorter rifle.
.30 Remington AR
Along with the new sister in the Cerberus group, Bushmaster, Remington also inherited the .450 Bushmaster cartridge, a case whose bolt face and overall length worked well in the AR, and delivered plenty of muscle. What was needed was a .30-caliber that would function in the short action.
The logical move? Neck the .450 down to .30-caliber. The result? The .30 Remington AR — a .30-caliber that would drive a 125-grain bullet at 2,800 fps and a 150-grain to almost 2,600 fps. That's 100 to 150 fps faster than the .30-30, long the standard by which whitetail cartridges are judged. I'm sure the .450 as well as the .30 Remington AR cartridges will soon find their way into levers and bolts, but for now, you can have either in a short, fast, semi-auto. Both bullet weights are currently loaded by Remington.
Another muscle load that has recently appeared that is delivering head-turning performance is the .458 SOCOM. The .458 SOCOM (.458 Special Operations Command) was reportedly given birth at an informal gathering of special-ops personnel, specifically Task Force Ranger, when the subject of stopping power came up. It seems it took multiple hits to permanently take the opposition "out of the game" in Mogadishu, Somalia. The consensus was a one-shot stop would sure be nice. Marty ter Weeme, founder of a company called Teppo Jutsu, L.L.C., went to work, and in 2000, a sledgehammer cartridge that would launch .45-caliber bullets from 250 to 600 grains from a standard-size AR-15 with a proper barrel and chamber was born — enter the .458 SOCOM.
Briefly, the result was a short, fat case (1.575-inch) with a very small rebated rim (.473-inch), minimal taper and a slight shoulder. The case headspaces on that minimal shoulder. It's an odd set of dimensions, but effective. The real cleverness in the design of the .458 SOCOM is that if you own an AR in .223, then nothing needs to be changed but the upper — same magazine as the .223, same buffer spring in the buttstock, same everything. Just get a .458 SOCOM upper available from Rock River Arms, Teppo Justsu or other custom builders, get loaded ammo from SBR Ammunition, Corbon or Reeds, and go.
6.8 Remington SPC
The 6.8 Remington SPC could just as easily have been called the .270 Remington Short, because that's what it is — a case that fires 115-grain .277 bullets at about 2,600 fps. It was created at the request of Special Forces personnel who wanted their targets to fall down fast and stay down at longer range, meaning they wanted a cartridge with more punch than they were getting from the standard-issue .223. The bottom line — it had to work on the existing AR action and use the standard lower.
Once again, case and cartridge length were the must-have parameters, so Remington went to an oldie, the discontinued .30 Remington, shortened it, blew it out, changed the shoulder and created a military cartridge that could be adapted to the AR. In the process, they gave hunters a great new choice that is accurate, light on recoil, and flat shooting enough for most whitetail hunters.
We have long appreciated cartridges like the .243, .260 Remington, 7-30 Waters, etc., for their low recoil, inherent accuracy and excellent performance. The 6.8 Remington SPC will fit exactly those parameters with a guarantee of available factory-loaded ammunition.