Only a few metric calibers have been really popular in the United States—6.5mm and 7mm—so the “Great 6mms” are relatively few in number. Some have long and storied histories, while others are just now making their own legends. Here’s a quick look at the best of this cohort.
Any discussion of great 6mm cartridges must start (some would say end) with the .243 Winchester. It debuted in 1955 and has been immensely and justifiably popular ever since. It is based on the .308 Winchester case, necked down with no other change.
Winchester’s strategy for the .243 was twofold and well thought out. First, the cartridge was designed for dual purposes: deer hunting and varmint hunting. (The company envisioned it as primarily a deer-hunting round, with occasional use on varmints.) Accordingly, the firm introduced two loads. The deer load had a 100-grain bullet, and the varmint load carried an 80-grain bullet. Company literature in 1955 described both bullets as “Soft Point.”
Second, it was chambered in the delightful Winchester Model 70 Featherweight, which was a major factor in the .243’s huge success. Not only did the rifle have a nice checkered American walnut stock, but also the light barrel was a handy 22 inches long. Twist rate was one turn in 10 inches, which handled the 100-grain deer bullets nicely. Accuracy was up to par, and shooters took to the rifle-cartridge combo like a duck, well, you know. They still do.
I have handloaded the .243 Win. for decades and have experienced no odd problems with it. My handloads for the round have all been for Missouri deer, and I can confidently recommend my favorite. It uses the ever-effective Hornady 100-grain RN InterLock with H4350 powder. Velocity is 2,827 fps, and out of my Browning A-bolt II, it groups into 1.10 inches. Some may scoff at the “old-fashioned” roundnose bullet, but it is a terrific game bullet, and I have never had to use a second shot to down a deer.
The .243 Win. wasn’t the only knife in the drawer, even if it was the sharpest one. Cartridge experimentation was in its heyday in the 1950s, and it was a rare cartridge case that didn’t get shortened, blown out, or necked up or down. Fred Huntington, founder of RCBS, developed a then-new 6mm cartridge by necking down the .257 Roberts case. He gave it a 32-degree shoulder and called it the “.243 Rock Chucker.”
In 1955, on the heels of the .243 Win., the .243 Rock Chucker was modified slightly by Remington and became the .244 Remington. It was essentially the Huntington cartridge, but with a 26-degree shoulder for easier case manufacturing.
The .244 Rem. was introduced in Remington’s Model 722 short-action bolt gun, and while the Model 722 was a very accurate rifle, it was rather plain. Its 26-inch barrel made the rifle a bit heavy for toting over hill and dale, plus the 1:12-inch twist limited bullet weights to 90 grains or lighter. (In the 1960s, Speer made a 105-grain RN just for the .244 Rem.) Remington surmised that the .244 would be used mostly as a varmint cartridge, with only an occasional application on deer-sized game, so the initial factory ammo was loaded with a 75-grain bullet. And just in case some hunter wanted to knock off a deer with his .244 rifle, the company also offered a 90-grain loading. Both were termed “Pointed Soft Point Core-Lokt” bullets.
Shooters greeted the .244 Rem. with a collective yawn and flocked to the equally new and elegant Winchester Model 70 Featherweight in .243 Win. The Model 70 .243 Win. was everything the .244 Rem. was not, and the .243 Win. remains a runaway hit to this day.
In an effort to salvage the .244 Rem., in 1963, Remington changed the name of the round to 6mm Remington and the barrel twist rate to 1:9 inches. And it made the “new” round available in the very attractive and accurate Model 700. A new 100-grain factory deer load completed the round’s metamorphosis.
While the .243 Win. continues to ride the crest of the 6mm-caliber wave, the tried-and-true 6mm Rem. remains a solid performer with today’s high-tech bullets, new powders, and fast-twist rifle barrels. While this excellent cartridge was almost doomed at birth, it has hung on, to the chagrin of deer, prairie goats, coyotes, and rock chucks everywhere. Many handloaders like the 6mm Rem.’s sharper shoulder and longer case, and while it’s not nearly as popular as the .243 Win., it is nonetheless a great 6mm round.
Interestingly enough, my history with 6mm rounds began with the 6mm Remington. In the 1970s, I had a Remington Model 700 BDL so chambered, and I took my first Texas whitetail with it. The powder charge I used then is lost to history, but the bullet was a Speer 90-grain SP. That bullet and Hybrid 100V powder recently grouped into a remarkable 0.44 inch in a Ruger Model 77R.
A new 6mm round blossomed in 2017, and it has already taken a position in the “Great” category. I’m referring to the 6mm Creedmoor, which is simply the 6.5 Creedmoor case necked down with no other change. It started as a popular wildcat before its approval by SAAMI. It’s easy to understand why it’s such an excellent performer.
All of the design criteria that went into the 6.5 Creedmoor that make it a top performer were also used in the development of the 6mm Creedmoor. It is chambered in many very good and some very inexpensive rifles, which have helped make it the hit that it is. My wife has a Ruger American in 6mm Creedmoor, and it is the only round that has been able to pry her away from her beloved .270 Winchester.
Her 6mm Creedmoor rifle is light and handy and shoots like a house afire, and recoil and muzzle blast are modest. With the super bullets and modern powders of today, I can’t imagine a better deer and antelope round.
Of course, handloading the 6mm Creedmoor is a reloader’s dream. Hornady’s 80-grain GMX and 103-grain ELD-X and the Speer 90-grain Hot-Cor all are accurate and deadly. While almost any combination of components seems to shoot well, my favorite powders are Hybrid 100V, Reloder 17, and Power Pro 4000MR. However, I must confess that Hornady’s factory loads shoot so well that the reloader is hard-pressed to better them.
One other fine 6mm round is the .240 Weatherby Magnum. Its case is bigger and its report louder, but it is deadly effective in the field. The .240 Wby. Mag. shoots the same cadre of 0.243-inch bullets as the .243 Win. and 6mm Rem., but it pushes them a little faster. The hunter can add about 100 to 150 fps of additional velocity to most game-weight bullets. That flattens trajectories somewhat and applies a bit more punch to the game.
Handloads are easy to prepare, and while my limited use of the .240 Wby. Mag. has not been on game, some loads stand out. The Barnes 80-grain Tipped Triple-Shock BoatTail sizzles with a velocity of 3,226 fps with a safe loading of VihtaVuori N550 powder, and the Speer 90-grain Hot-Cor can easily achieve 3,115 fps with VihtaVuori N160. Both bullets produce deer-slaying accuracy.
Another cartridge that deserves mention is the relatively new 24 Nosler. It’s small, and its availability is limited, but its accuracy and ballistic performance really qualify it for the “Great” category.
The cartridge was developed by Nosler’s Mike Lake, and it was approved by SAAMI in 2017. This makes it a “factory” cartridge, although no factory ammo is available, and guns chambered for it are all custom jobs. That’s only a minor impediment for serious riflemen.
The 24 Nosler is exceptionally accurate and mild mannered and has cleanly taken numerous midsized big-game animals. It is based on the previous 22 Nosler and has two features to make it compatible with AR-type rifles: a slightly rebated rim that is the same diameter as the .223 Remington and an overall cartridge length set at 2.26 inches, the same as other AR rounds.
I tested a bolt-action handgun in 24 Nosler last year and was so impressed with the round that I had a Remington Model 700 originally in .223 Rem. rebarreled to 24 Nosler with a stainless-steel, three-groove PAC-NOR barrel.
The 24 Nosler is a terrific performer, so don’t let its small size fool you. It hits way above its weight class. But since there is no factory ammo, 24 Nosler shooters must handload. This is fortuitous, as it is a delight to reload and seems to like just about all the bullets I’ve tried in it. Powder selection is easy: Just stick with CFE 223 and all will be right with the world. It is accurate, produces good velocities, and the copper eraser stuff in this powder makes barrel cleaning a breeze.
The benchrest crowd has not been overlooked in the 6mm derby, and one cartridge literally rewrote the record book. This is the “Great” short, fat 6mm PPC that was developed by Dr. Louis Palmisano and Ferris Pindell. The pair developed the .22 PPC in 1975, and the 6mm PPC followed in 1987. The .222 Remington, introduced in 1950, was top dog in benchrest circles until the advent of the PPCs, after which, the 6mm PPC was used by virtually all serious benchrest competitors. Its accuracy is simply phenomenal, and it makes a superior varmint cartridge. I had a heavy-barreled Sako single shot in the 1970s, and it shot like almost all 6mm PPCs: great.
6mm BR Remington
Another round that was designed for the steel shooters is the 6mm BR Remington. In the 1970s, Remington experimented with a .308-sized case that was about 1.5 inches long and had a small primer pocket (like the PPCs). Many shooters necked the BR case down, and a 6mm version ultimately became the 6mm BR Remington. Factory loads were available, and it was moderately popular for both varmint and deer hunting and target shooting. It gave dependable accuracy and high velocities.
I had a Remington Model 700 BDL Varmint rifle rebarreled with a heavy stainless-steel barrel chambered for the round, and it lived up to its reputation. I tested dozens of loads, mostly with benchrest bullets, and the rifle shot well. Top loads used H322, W748, and Reloder 7 powders with 65-, 68-, and 75-grain match bullets. The current reincarnation of this round is the 6mm BR Norma, with essentially the same case dimensions.
The newest 6mm factory round is the recently announced 6mm ARC (Advanced Rifle Cartridge). Brought out by Hornady just a few months ago, this moderate-sized round is based on the 6.5 Grendel and shares similar rim and body dimensions. Party-poopers will gleefully point out that the 6.5 Grendel was based on the 6mm PPC case necked up, and here it is necked back down to 6mm. But no matter, new is new.
Claims for the 6mm ARC are that it is better in every category. It is “advanced” for the AR platform. It is versatile, in that it is suitable in both ARs and mini-bolt guns for hunting, personal protection, and target shooting. Its design uses propellants efficiently. And its performance is effective with a variety of bullets. Low recoil is also noted. So far, I have not laid my eyes or hands on a single 6mm ARC cartridge or rifle, so I will withhold judgment until I test one. But on paper it looks promising.
Benchrest (BR) shooters will go to almost any length to shave 0.001 inch off of their aggregate average, and there is a diverse assemblage of 6mm wildcat rounds for BR shooters. These developments are interesting, and the supreme accuracy achieved by several of the wildcat cartridges make them worthy of mention here. Obviously, they are not nearly as popular as the 6mm hunting cartridges.
In the 1970s, the .222 Rem. Mag. was necked up to 6mm and called the 6x47. No factory rifles or ammo was available, but for a while, Federal offered nickel-plated 6x47 cases. It is reported to be very accurate, but its aura is eclipsed by the shadow of the 6mm PPC.
Another interesting development is the 6mm Dasher that was developed by Al Ashton and benchrest gunsmith Dan Dowling. It is formed by using a shortened .22-250 Remington case, and it has thinner walls for increased powder capacity and the “Ackley improved” shape. It has had moderate success in various target venues.
Wildcatters have had a field day with the 6mms, and the list of their creations is long. They run the gamut from tiny benchrest numbers to those with larger cases that essentially duplicate many factory rounds. Some examples include the 6mm-204 and the 6x45. Based on the .204 Ruger, which was created from the .222 Rem. Mag., the 6mm-204 essentially recreates the 6x47. The 6x45 is the .223 Rem. case necked up, made especially for ARs. Today’s fast-twist .223s and heavy bullets have made it effectively obsolete.
I doubt that the book on the “Great” 6mm cartridges is closed, and future developments may add new chapters, to the delight of many shooters.