The Fastest Cartridge You’ve Never Heard Of

In August of 1964, Guns & Ammo published a cover story detailing what the magazine’s editors enthusiastically dubbed “the world’s hottest .22!” The wildcat cartridge could launch a 15-grain bullet an astounding 6585 feet-per-second (fps), over twice as fast as a .30-06 Springfield and six times as fast as a .22 LR.

Led by the magazine’s technical editor, Bob Hutton, a team of engineers created the record-breaking “.22-.284” cartridge by necking down the recently released Winchester .284 to .22 caliber. As far as we know, it’s still the fastest small arms cartridge to achieve practical accuracy.

Exploding Bullets

Unsurprisingly, the resulting hot rod faced a few issues out of the gate. “We soon found that the .22 caliber bullets couldn’t stand the 4300 fps without exhibiting all sorts of problems,” Hutton reported. Bullets printed keyholes in paper at 100 yards, and many never reached the targets at all because the jacket “blew up completely.”

Dr. Edgar L. Eichhorn from Pasadena, California, soon came to the rescue. He constructed 31- and 50-grain bullets with extra heavy jackets that could withstand the high velocities and 270,000 revolutions per minute.

For lighter projectiles, Hutton’s team turned to iron bullets (yes, iron!) loaded in Remington’s now-defunct .22 Rocket Short. The bullets were shot from two barrels made by P.O. Ackley, one with a 1:14 twist rate and another with a 1:24 twist rate. “Twist rate” describes the number of times a bullet spins per inch of barrel. A “1:14” barrel spins a projectile once every 14 inches.

With 54 grains of 4064 powder, those 15-grain bullets could travel 5,485 fps. With 50 grains of 4227 powder, they hit top speeds of 6585 fps. More impressively, those bullets posted two-inch groups at 100 yards, which is (believe it or not) considered accurate enough for the U.S. military’s M4 rifle.

The images that accompanied the article show a 12-ounce can of water that was hit so hard that the bottom of the can formed to the contour of the table below it.

Practical?

The potential benefits of such a cartridge for varmint hunters are obvious. The iteration of the .22-.284 that used a 31-grain bullet shot almost perfectly flat: sighted in one inch high at 100 yards, the projectiles also tore through paper one inch high at 200 yards. At 300 yards, the tiny bullet had only dropped seven inches below the target.

What’s more, those 31-grain bullets produced two-inch groups at 300 yards, which offers more than enough precision for most hunting purposes.

Caliber Battle readers will recall that super-fast cartridges often produce debilitating recoil energy, but by all accounts, the .22-.284 is easy to shoot in a reasonably heavy rifle.

So, why aren’t varmint hunters using Hutton’s version of the .22-.284 today?

Barrel life is the main deterrent. The .22-.284 is what ballisticians call an “overbore cartridge.” Overbore cartridges feature a large case volume coupled with a small bullet/bore diameter (hence “over-bore”). The barrel’s volume isn’t large enough to accommodate a large amount of burning powder, high pressures, carbon, and copper. These elements eat away at the barrel more quickly, especially in the “throat” of the barrel.

“The volume of powder that you’re burning is what ends up burning out barrels,” Jake Burns told MeatEater. Burns is the Product Development Engineering Manager for Federal Premium’s centerfire rifle cartridge division. “You have less surface area in the bore for that powder and pressure to disperse.”

The rate of barrel deterioration depends primarily on the barrel’s construction, so Burns hesitated to offer specific predictions about the .22-.284. But he did estimate that while a normal 6.5 Creedmoor barrel might last 7,000 rounds, hotter cartridges might wear out a barrel in 2,000 rounds.

Burns also explained that overbore cartridges aren’t often pursued by ammo companies like Federal because barrels with effective twist rates aren’t easy to find. The faster a projectile moves, the slower the twist rate must be to keep the bullet from spinning so fast that it breaks apart. The 1:24 twist barrel Hutton used is almost unheard of, and even the 1:14 would be difficult to find.

“We look at it as a balance. We know we could take a .300 Win. Mag. case and neck it down to .22-caliber. But there are tradeoffs,” Burns said. “That’s why you don’t see more of this stuff commercially.”

Carrying the Flame(thrower)

Despite the .22-.284’s disadvantages, the quirky old wildcat isn’t quite dead yet. Bob Coles is the leader and, from what I can tell, the only member of this small band of aficionados. He set out in 2014 to recreate Hutton’s design, and he recorded his experience in a detailed article and a more recent video. He’s also published a full book of load data, which is available on his website.

Coles stayed away from the ultra-light bullets and opted instead for a 75-grain Hornady A-Max bullet. Fifty-three grains of H1000 powder produced about 3,500 fps of velocity and excellent 0.25-inch groups at 100 yards. With a 230-yard zero, the bullet hit 1.3 inches high at 100 yards and 3.5 inches low at 300 yards.

Coles’ Mauser-action rifle features a heavy, stainless-steel barrel with a 1:9 twist. It wouldn’t be practical to carry through the woods, but according to Coles, it makes an excellent varmint gun. He’s taken coyotes, crows, and woodchucks, and he says the 75-grain bullet wipes them out. “When you hit them at over 3,000 feet-per-second, they explode. The classic red mist,” he said.

To those concerned about barrel life, Coles compared barrels to car tires. “They’re meant to be used and replaced, so I’m not worried about that,” he said. He also noted that as long as shooters are careful not to let the barrel get too hot, they can expect about 1,000 rounds before accuracy decreases. Even in that case, accuracy might not drop enough to warrant a new barrel.

Coles’ barrel has yet to wear out. When it does, he plans to start experimenting with super-light bullets like those Hutton used. But he thinks new all-copper bullets like Federal’s Trophy Copper will hold together just as well as Remington’s old iron pills.

Last Shot

The .22-.284 likely won’t see a resurgence any time soon. Other cartridges like the .22-250 and the .220 Swift do everything a varmint hunter needs without burning out barrels quite as fast.

But as with many wildcat cartridges, the .22-.284 pushed ballistics forward. Burns said that he and his team at Federal pay close attention to what’s popular among wildcatters.

“We’re often looking at what the end-users are doing in the industry. If people find benefits in x, y, z cartridge, we ask whether we should be doing something along those lines that gives the user those benefits,” he said.

Hutton responded to critics by pointing out that their test demonstrated the advancements that needed to be made in bullet construction, the possibility of practical accuracy in a bullet traveling 6,000 fps, and the benefits of new electronic ballistic computers.

“Rifles are available over the counter today that 15 years ago were available only as the wildest wildcats,” he noted.

The .22-.284 didn’t make that jump, but Hutton’s risk-taking mindset has underscored every advance in bullet, powder, and case design to date. We can thank folks like him every time we use those tools to harvest the game we love to pursue.