10 Wildcat Calibers That Made the Grade

From mild to wild, here are the most popular custom-made cartridges of all time

Mike Dickerson collected this gray fox in Texas using a Savage rifle chambered for the round.
The .22-250 Remington, which began life as a wildcat, has become one of America’s favorite varmint and predator rounds. The author collected this gray fox in Texas using a Savage rifle chambered for the round.Mike Dickerson

Wildcat, or custom-made cartridges, have been a part of the American shooting scene for about as long as there have been metallic cartridges. Most were created by gunsmiths or ardent hand loaders trying to improve upon an existing cartridge or create a round to meet a specific need. Wildcats likely number in the thousands by now, but relatively few have enjoyed long-term success compared to factory cartridges. Of this number, even fewer were ever legitimized as factory cartridges, as were the selections presented here.

Since there have to be rules to the game, our list excludes some proprietary cartridges which some people commonly but mistakenly think of as wildcats. Similarly, there are some entries that many people believe originated as factory offerings, but actually did not. This list is composed of cartridges that started out as true wildcats but were subsequently adopted as standard factory loads. Some became spectacularly successful. Others have occupied a much narrower niche. From mild to wild, here are our choices for 10 wildcats that made the grade.

1. .22 Hornet

Hornady 22 Hornet Ammo
The .22 Hornet, based on the obsolete black powder .22 WCF, has been popular for a century and is still loaded by most ammo makers today.Hornady

If you measure the success of a cartridge by its longevity, the diminutive .22 Hornet has to rank near the top of the list. Although it’s not as popular as it once was, and has been eclipsed in performance by more modern cartridges, this varmint and small game specialist has been with us for a century now and is still chugging along.

The names most closely associated with development of the .22 Hornet are Grosvenor Wotkyns and Townsend Whelen, Army officers and avid shooters. In their quest for a varmint cartridge with higher velocity and greater reach, they experimented with the obsolete .22 WCF, a black powder cartridge, and began loading it with smokeless powder. The end result was a round that pushed little bullets at speeds approaching 3,000 fps (feet per second). Whelen helped to popularize the round in his writings for Outdoor Life at a time when America was experiencing a surge in popularity in varmint shooting. Although the round has given way to more potent varmint cartridges, it remains popular with many shooters thanks to its mild recoil and report. Most major ammo makers still offer .22 Hornet ammo in bullet weights ranging from 30 to 45 grains with muzzle velocities of 2,665 to 3,150 fps.

Winchester offers three .22 Hornet loads, from 35 gr. to 46 gr. Browning’s .22 Hornet round, the 35 gr. BXV Predator & Varmint, has a muzzle velocity of 3,100 fps.

2. .22-250 Remington

Federal Premium 22-250 Ammo
Based on a necked-down Savage 250/3000 case necked down to .224 caliber, the .22-250 Remington went mainstream in 1965 when Remington introduced it paired with the then-new Remington 700 rifle.Federal Premium

Grosvenor Wotkyns pops up on our list again as of one of several people who experimented in the late 1930s with rounds based on the Savage 250/3000 case necked down to .224 caliber. The resulting cartridge, then called the .22 Varminter, had a steeper 28-degree shoulder angle than the parent case and came close to matching .220 Swift performance, but it did so in a more efficient manner. The round remained a wildcat until Remington introduced it in 1965 as the .22-250 Remington and paired it with the then relatively new Remington 700 rifle.

It was a marriage made in heaven—or possibly hell, from a coyote’s point of view. The .22-250 went on to become a much-beloved varmint and predator round, and remains one of the most popular choices for coyote hunters. It shoots flat, hits hard and bucks the wind decently enough to be a good choice for prairie dogs, but as I’ve experienced first-hand, it’s perfectly capable of taking deer with the right bullets. Matched most often with rifle barrels having a relatively slow 1:12 twist, factory ammo is commonly loaded with lighter bullets weighing 35 to 55 grains. Muzzle velocities are typically in the 3,600 to 4,450 fps range.

In .22-250 Remington, Winchester offers six loads, from their 38 gr. VarmintX to the 64 gr. Power Point. Browning offers a 50 gr. BXV Predator & Varmint, with a 3,400 fps muzzle velocity.

3. .243 Winchester

Federal Premium .243 Winchesteer ammo
The former wildcat .243 Winchester succeeded where the .244 Remington failed because rifles chambered for the .243 Win. had faster rates of twist and better stabilized heavier bullets.Federal Premium

One of the many attributes of the .308 Winchester is the fact that its case has served as the basis for a host of other cartridges of both the factory and wildcat variety. One of these is the .243 Winchester, which many sources list as having been launched in 1955 by Winchester for the Model 70 rifle, but it was preceded by what former Field & Stream shooting editor Warren Page called his .243 Page Pouper (or Pooper, depending on who’s telling the story). The competing .244 Remington was introduced at about the same time as Winchester’s round, but flopped so badly that Remington later renamed it the 6mm Remington.

The .243 Winchester went on to become one of the most popular cartridges of all time. This was partly due to its ability to take deer-sized game with rifles producing very mild recoil, and partly due to the fact that rifles in .243 Winchester had a faster rate of twist than rifles in .244 Remington, enabling them to better stabilize heavier bullets. Today, every major ammo maker offers .243 Win. ammo, most commonly in bullet weights ranging from 50 to 100 grains, launched at velocities ranging from a bit more than 2,900 fps for heavier bullets to 3,850 fps for the lightest bullets.

There are 10 loads available from Winchester, including a 95 gr. Deer Season XP with muzzle velocity of 3,100 fps. Browning’s .243 Win 65 gr. BXV Predator & Varmint has a 3,400 fps muzzle velocity, and their 97 gr. BXR Rapid Expansion, leaves the barrel at 3,100 fps.

4. .257 Roberts

Hornady .257 Roberts
Developed by Ned Roberts in the 1920s, the .257 Roberts is today considered the mildest of the most popular quarter bores.Hornady

A wildcatter named Ned Roberts started to experiment with .257-caliber cartridges in the 1920s, modifying a 7x57 case by giving it a long neck and a 15-degree shoulder angle. It was Townsend Whelen who reportedly named the cartridge the .25 Roberts, and Remington renamed it the .257 Roberts when the company took the cartridge mainstream in 1934 even though the Remington design differed dimensionally from Roberts’ creation.

The .257 Bob has developed a small but loyal following over the years, thanks in part to its relatively gentle recoil. Although it is considered one of the mildest of the most popular quarter bores, it is a very capable deer cartridge when loaded with proper bullets, but it isn’t exactly easy to find on store shelves. Ammo makers who still produce the cartridge include Hornady, which offers a .257 Roberts +P load with a 117-grain SST bullet and a muzzle velocity of 2,945 fps. Winchester still sells a 117-grain Power Point load. Remington no longer lists the cartridge, but Nosler offers four different +P loads with 100-115 grain bullets, and HSM lists three loads, including one with a 75-grain V-Max bullet suitable for predators and varmints. As with many cartridges, hand loaders can boost the performance of the round, but optimal results are best achieved with 24-inch barrels.

5. .25-06 Remington

Hornady American Whitetail Ammo
Versions of the .25-06 Remington had been around as wildcats for half a century before Remington introduced the round in 1969. Based on a .30-06 Springfield case necked down to hold a .257 caliber bullet, it is a great flat-shooting round for open country.

A host of wildcatters experimented with .257 caliber bullets seated in necked-down .30-06 Remington cases for fifty years before Remington officially introduced the .25-06 Remington in 1969. Although it has been commonly used on everything from prairie dogs to elk, the round appealed to open-country hunters pursuing deer and pronghorn antelope due to its relatively high velocity and flat trajectory. Zeroed at 200 yards with a 100-grain bullet, the bullet strikes less than six inches low at 300 yards.

The .25-06 speaks with authority, but is milder recoiling than the .30-06 Remington. While it’s slower than the .257 Weatherby Magnum, the .25-06 is still a speed demon compared to many other deer cartridges that use heavier bullets, but you’ll need barrels longer than 22 inches to realize the round’s true potential. Federal lists muzzle velocities at 3,220 fps for a 100-grain Nosler Ballistic Tip round and 3,030 fps for a 115-grain Nosler Partition load, while Hornady’s 117-grain Superformance SST round steps out at 3,110 fps. Deer tagged with any of these rounds aren’t likely to notice the differences. The .25-06 is a just about perfect for hunting deer-sized game, yet it remains somewhat under-appreciated by much of the shooting public who buy a lot more rifles chambered for cartridges like the 6.5 Creedmoor and .270 Winchester.

Winchester’s offers five loads in .25-06 Rem, from their 85 gr. Ballistic Silvertip to the 120 gr. Power Point. The 117 gr. Deer Season XP has muzzle velocity of 3,100 fps.

6. 6.5-284 Norma

Nosler 6.5 284 Norma
The 6.5-284 Norma once set a 1,000-yard world record as a wildcat. It is based on the unsuccessful 284 Winchester.Nosler

If you’re a fan of the 6.5-284 Norma cartridge, you likely already know that factory ammo can be hard to find. If you look for it on the web sites of Federal, Hornady, and Winchester, you won’t find it, and that’s a shame because the 6.5-284 is one of the best short-action cartridges to ever slide into a receiver. The 6.5-284 has been around as a wildcat since shortly after the unsuccessful .284 Winchester was announced in the early 1960s. Benchrest shooters necked the cartridge down for 6.5mm bullets and, at one point, set a 1,000-yard world record with the wildcat.

Norma saw the value of the cartridge and brought it out as a factory offering in 1999. Happily, Norma still loads the round, as does Nosler. Like many other 6.5 cartridges, the long, high ballistic coefficient bullets used in the 6.5-284 hit a sweet spot. They tend to have high sectional density for good penetration and are wonderfully accurate. Loaded with proper hunting bullets, the round is effective on game up to and including elk. It’s easy to make a case, depending on how you crunch the numbers, that the 6.5-284 Norma outperforms rounds like the 7mm-08 and the .308 Win., with only moderate recoil, and it even slightly outruns the popular 6.5 Creedmoor with bullets of comparable weight. Norma currently loads three rounds, including a 130-grain target round and a 156-grain Oryx hunting load. Nosler produces eight different loads with match and hunting bullets ranging from 120 to 140 grains.

7. 7mm-08 Remington

Federal Premium 7mm-08 ammo
Based on a necked-down .308 Win. case, the 7mm-08 is a relatively soft-kicking round suitable for everything up to and including elk.Federal Premium

Americans have long had a love affair with .30 caliber cartridges, but there’s not a lot they can do on medium-sized game that can’t be done with the 7mm-08 Remington, at reasonable distance, with significantly less recoil. Based on the 7mm/08 wildcat, the 7mm-08 Remington, as introduced by Big Green in 1980, uses a .308 Win. case that has been slightly lengthened and necked down for a .284 bullet. In a basic ballistic sense, it is very much the equal of the respected 7x57 Mauser, and hand loaders can work magic with the round.

A wide range of factory ammo is available to suit a variety of needs. Federal currently offers nine loads with 120-150 grain bullets, and Hornady produces 11 loads in an even wider range of bullet weights. Winchester and Remington offer five and four loads, respectively. If you’re looking for one load to do it all for game up to and including elk, good choices would be Federal’s load with a 140-grain Nosler Partition bullet and a muzzle velocity of 2,800 fps, or Hornady’s Precision Hunter round with a 150-grain ELD-X bullet and a muzzle velocity of 2,770 fps. All things considered, including ballistic performance, terminal effectiveness, recoil, and rifle and ammunition availability and selection, the 7mm-08 has a lot going for it.

Browning’s .7mm-08 Rem 144 gr. BXR Rapid Expansion has a 2,800 fps muzzle velocity.

8. .280 Ackley Improved

Nosler .280 Ackley ammo
The .280 Ackley Improved is based on a .280 Remington case, but holds more powder and produces faster muzzle velocities.Nosler

The .280 Ackley Improved, created by P.O. Ackley and Fred Huntington, was based on a .280 Remington case with a 40-degree shoulder angle. This allowed for more powder capacity and faster muzzle velocities, by about 100 fps for most bullets, over the parent round. The wildcat went legit, thanks to Nosler, when it was accepted by SAAMI in 2008. Although the round isn’t exactly a household name, more rifles are now being chambered for the cartridge. It’s relatively easy to convert .280 Rem. chambers to .280 Ackley Improved, and you can fire form brass for reloading by firing .280 Rem. cartridges in a .280 Ackley Improved rifle.

In performance, the round is a much closer match to the potent 7mm Remington Magnum, particularly when comparing factory ammo, than the .280 Remington. Federal’s 150-grain Nosler Ballistic Tip 7mm Rem. Mag. load has a muzzle velocity of 3,025 fps. Zeroed at 200 yards, the bullet drops 6.4 inches at 300 yards. In contrast, Nosler’s 150-grain AccuBond Long Range 280 AI load leaves the muzzle only 95 fps slower and drops only three-tenths of an inch more at 300 yards. The 280 AI has the added virtue of producing a bit less recoil than the magnum. Nosler still loads more ammo in the cartridge than anyone else, in bullets ranging from 140-160 grains, and Federal loads one round with a 168-grain Berger Hybrid bullet.

9. .35 Whelen

Federal Premium 35 Whelen Ammo
The .35 Whelen, conceived as a poor man’s magnum for dangerous thin-skinned game, will handle any North American game animal.Federal Premium

The .35 Whelen may bear the name of Col. Townsend Whelen, but Whelen himself credited James V. Howe with developing the wildcat, which was created by necking up a .30-06 Springfield cartridge to accept a .35 caliber (.358 in.) bullet. My research hasn’t revealed whether Whelen spent a lot of time hunting with the cartridge, which was characterized early on as a sort of poor man’s magnum for taking thin-skinned dangerous game, but Elmer Keith did, taking animals up to and including a very large brown bear in Alaska. This potent medium-bore cartridge remained a wildcat for about 60 years until Remington first offered it as a factory cartridge in 1988.

The .35 Whelen isn’t exactly a long-range cartridge, as lower-BC bullets generally limit effective range to several hundred yards with most loads. The cartridge has, however, earned a reputation as a legitimate thumper over the years, delivering energy that isn’t too terribly far behind some .375 H&H Magnum loads and proving its worth on the largest of North American game. Hand loaders can wring maximum performance out of the cartridge, but there’s plenty of factory ammo from Barnes, Nosler, Hornady, Federal, and Remington, among others, that will get most any job done handily with proper bullet selection. The Hornady 200-grain Superformance load, for example, exits the muzzle at 2,910 fps, producing an impressive 3,760 foot pounds of energy. That’s only about 200 foot pounds behind some .375 H&H Magnum loads with 250-grain bullets.

10. .458 Lott

Hornady .458 Lott ammo
Capable of taking the most dangerous game in the world, the .458 Lott was created by an American hunter who had a near-fatal encounter with a Cape buffalo while hunting with the .458 Winchester Magnum.Hornady

It’s difficult to sort reality from rumor when it comes to American writer and experienced African hunter Jacques “Jack” Lott—including the question of whether or not he ever worked for the CIA—but history is clear on the fact that he had caught a nearly fatal dose of Cape buffalo while hunting in Mozambique in 1959 with the .458 Winchester Magnum. That experience left him disenchanted with the round, and he would go on to design a more powerful .458 cartridge that would, by the early 1970s, bear his name. That cartridge, which he is said to have first sketched out on a napkin, was the .458 Lott, and it will handle anything that walks on this planet.

Like the .458 Win. Mag., the cartridge is based on the .375 H&H Magnum case, but is longer, at 2.8 inches versus 2.5 inches for the .458 Win. Mag, allowing for more powder capacity and upgraded performance. Examples of current factory offerings include three Federal Cape-Shok loads using 500-grain bullets, including the Trophy Bonded Bear Claw, the Trophy Bonded Sledgehammer Solid and the Woodleigh Hydro Solid. Velocities are listed at between 2,250 and 2,300 fps, while energy at the muzzle for the most potent load is a whopping 5,873 foot-pounds. Hornady offerings include a 500-grain DGS (dangerous game solid) and a DGX Bonded load, which employs a copper-clad steel jacket and lead core bonded to the jacket. If dangerous game is on your agenda, the .458 Lott is a great choice of companion.