Minimum-caliber rules may prevent some resident hunting with rimfire rifles. Assuming everyone obeys the law, they do keep accomplished varmint hunters from using Swifts and .22-250s for deer, mandating instead that marksmen choose more appropriate rounds -- perhaps the .25-20? Someone must have seen the absurdity and suggested energy minimums: My home state of Washington specifies 900-foot pounds at 100 yards.

Truly, most big game hunters serious enough to buy a license will choose a killing cartridge. In the field, I've seen lots of rifles with crude sights, fogged scopes, rough military triggers, badly fitted stocks, eroded bores and malfunctioning magazines. Many had not been sighted in and were carried by unskilled, undisciplined shooters. But I've yet to see a rifle chambered for a cartridge that would not cleanly kill big game.

What of the 6mms? If the .223 is too light for pronghorns, why is the .243 approved for elk? At 3,150 fps, velocity for the 55-grain .223 bullet equals that of a 90-grain .243 bullet. Muzzle energies: 1,200 and 2,200 foot-pounds. But a bull elk outweighs a pronghorn buck 6 to 1.

We think of 6mm (.243) cartridges as modern. But the first of them appeared in the 1895 Lee straight-pull bolt rifle. Also known as the .236 Navy, the 6mm Lee Navy was a semi-rimmed round chambered in about 15,000 military rifles. Its 112-grain bullet ambled along at only 2,560 fps but could have been driven much faster had modern powders been available. That bullet was very long; rifling twist was 1:7-1/2. The 6mm Lee Navy died in 1935. Shortly thereafter, the .220 Swift was born of the same case.

Not until 1955 would American factories again produce 6mm ammunition. But in the early 1920s, Holland and Holland gave British shooters two new cartridges: the .240 Flanged Nitro Express and the .240 Belted Nitro Express (.240 Apex). The first was a rimmed case, the second a rimless belted. Both were loaded with 100-grain .245 bullets, the belted version to 3,000 fps for bolt rifles, the rimmed cartridge to 2,900 for doubles. Purdey introduced, in 1921, its .246 Flanged cartridge with 100-grain .253 bullets at 2,950 fps; and in 1923, the .242 Vickers Rimless Nitro Express appeared, giving 100-grain .249 bullets 2,800 fps. If the British were stuck on one bullet weight, they changed bore diameters at whim. American handloaders would not have put up with such foolishness!

(Incidentally, the term Express is a Purdey creation, dating to 1856. Originally, it was Express Train, a designation of extra power, but the second word was later dropped. To British riflemen, Express means what Magnum does to American shooters. Neither term has been adequately defined. Neither has any descriptive value beyond advertising.)

In Europe, German designers Halbe and Gerlich made both rimmed and rimless cases for the .244 Halger. Basically a 6.5x57 case, it was a modern shape for the 1920s. Limited by the powders of the day, it did not achieve cataloged velocities.

In 1955, Holland and Holland came along with the biggest six of all: the .244 H&H Belted Rimless Magnum. The .375 case necked down, this bottle-size brass was originally stuffed with cordite but came close to its sizzling potential only with slow progressive powders like H-570. Even then, 3,500 fps with 100-grain bullets proved elusive. Certainly the cartridge is inefficient, though it was one of the flattest-shooting of its time.

After the Lee Navy cartridge faded, little was done commercially with 6mm cartridges in this country. But just after World War II, wildcatters got busy. One of their first creations was the 6mm International, based on the .250 Savage case. In the shortened Donaldson version with a 30-degree shoulder, or in the later long-necked Remington configuration, it was and is a good cartridge.

Another noteworthy round was the Page Pooper, developed by writer Warren Page and Remington's Mike Walker. A .308 case necked down to .243, it was the forerunner of Winchester's .243. It had a sharper shoulder and longer neck. Later, Mike Walker also worked on the 6x47, a .222 Magnum case necked up to .243. It has since been supplanted by the 6x45 on the ubiquitous .223 case.

Among the best of the post-war wildcats was Fred Huntington's .243 Rockchucker. Based on the .257 Roberts case, this hot number predated Remington's similar 6mm. At his reloading-tool firm of RCBS (rock chuck bullet swage), Huntington also developed a .243 RCBS on the .308 case.

Later there were 6mms on the .30-30 case, the .303 British, .30-40 Krag, .30-06. The latest and most publicized of .243 wildcats is the 6mm PPC, developed by benchrest shooters Louis Palmisano and Ferris Pindell in 1975. It's a short, fat little cartridge, formed from .220 Russian brass. Like many .243 wildcats, it has limited application afield, but it is fiercely competitive on the range.

Back to 1955. As Holland & Holland was hawking its .244 Belted Rimless Magnum in Europe, Winchester unveiled a new .243 and Remington its .244. The .243 is simply Winchester's .308 case necked to accept .243 bullets. Remington's round is the .257 Roberts case choked to .243 and given a sharper 26-degree shoulder. Winchester's case has slightly less capacity, and the long 20-degree shoulder has been criticized as an invitation to case stretching. But effective case capacity in short actions is pretty close to the same, because bullets must be seated deeper in the .244 Remington case. And I’ve not had any case-stretching issues with the .243.

There were differences in factory loadings early on. The .243 was capped with 80-and 100-grain bullets, the .244 with 75-and 90-grain bullets. More importantly, rifles chambered for the .243 had a 1:10 twist, compared to a 1:12 for those in .244. That reflected differences in company philosophy: Winchester had intended its new round as a varmint/big game cartridge, while Remington considered the .244 primarily a wind-bucking panacea for 'chuck, fox and coyote hunters. Word got out that the 1: 12 twist wouldn't stabilize 100-grain bullets hunters preferred for deer. The .243 rocketed to fame; the .244 fell off its launch pad.

I owned an early Remington .244, an accurate 722-bolt rifle. It shot as well with 100-grain bullets as with lighter ones. Bullet shape and length, not just weight, determine how bullets will stabilize with any given twist. Round-nose bullets, shorter than spitzers, generally stabilize easier. High velocity helps bullets stabilize, too. Though Winchester's rifles of the late fifties -- its lever-action 88, auto-loading 100 and bolt-operated 70 -- were better equipped for heavy bullets than the Remington’s in .244, some 1:12 barrels shot a variety of bullets well. Besides the 722, Remington marketed its slide-action 760 and, for a time, its 742 auto-loader in .244. In 1963, Remington introduced a new cartridge: the 6mm. Factory-loaded with 80-, 90-and 100-grain bullets, it replaced the .244. Except for bullet choices, it was also the same as the .244. The two cases are identical and may be interchanged. The new name was a marketing ploy and coincided with a change to 1:9 twist in Remington 24-caliber barrels. Winchester's round had a head-start by this time, and a daunting reputation. Still, the 6mm Remington has become popular.

At first, the 6mm appeared to beat the .243 ballistically by quite a margin. Part of the reason was that .243 factory loads were often chronographed in 22" barrels, not the 26" barrels used for 6mm testing. Too, some early Winchester cartridges were loaded to 47,900 psi, vs. 51,100 psi for Remington's 6mm rounds. When both cartridges are hand-loaded with IMR-4350 to 50,000 psi with 100-grain bullets, both generate about 3,100 fps from a 26-inch barrel. The 6mm has a slight edge.

The only other factory-loaded domestic 6mm suitable for big game is the .240 Weatherby. Introduced in 1968, it's available with 90- and 100-grain bullets at advertised velocities of 3,500 and 3,395 fps. Loaded to equal pressures from barrels of the same length, it shades the .243 Winchester and 6mm Remington by about 200 fps. The belted .240, with its .30-06 size head, is neither parent nor offspring of any other case. It's chambered only in Weatherby Mark V rifles.

Well aimed, these 6mms can certainly kill big animals. One hunter reported killing a grizzly and a polar bear with his .243! But many have argued they're not practical even for deer; more riflemen question their use on elk.

After the .243 had been afield a season, a survey recorded 83 kills, most of which were on whitetail and mule deer at ranges averaging 140 yards. Of the 83, 60 were instant, one-shot kills; 13 animals moved off but dropped within 200 yards; only six had to be trailed. Another survey recorded mule deer, pronghorns and black bear shot with the .243 at ranges to 500 yards. None moved from where they were hit, and only a few required a finishing shot.

There are reasons for such rosy reports. First, the .243 and 6mm both shoot very flat, minimizing errors in range estimation. Secondly, they're pleasant to shoot; consequently, hunters shoot them more often and with more care to shooting well than they do hard-kicking rifles that promote flinching. Lastly, the surveys no doubt included experienced hunters -- gun writers and perhaps guides who would provide a lot of information quickly. Better-than-average shot placement resulted.

While the hunting-class 6mms generate plenty of foot-pounds of energy, most of that is due to the bullets' speed. In pounds-feet, no 24-caliber bullet fares very well. Using the 180-grain .30-06 bullet as a standard, we find factory-listed velocity at 2,700 fps, energy at 2,910 foot-pounds. The 100-grain factory load in a .243 chronographs 3,070 fps, generates 2,090 foot-pounds -- a faster bullet with 72 percent of the '06's energy.

Now let's calculate pounds-feet: bullet weight (grs.) / 7,OOO x velocity (fps). The .30-06 yields 69.4 pounds-feet, the .243 not quite 43.9, or only 63 percent of the standard. In animals like elk, with thick hide and hair, heavy bones and great muscles, bullet weight and size count! While pounds-feet is no measure of killing power, it helps complete a picture skewed by velocity in the calculation of foot-pounds.

To destroy vital organs, the bullet must penetrate. To penetrate, it must retain enough mass after mushrooming to overcome the pull of tissue slowing it down. When it gets to the vitals, it must be big enough and heavy enough to make a fatal wound and keep going. Whether it stops just under the far hide or pops through is of academic importance, perhaps relevant to the bullet maker, but certainly dependent on shot angle, distance, velocity and what bones and muscles impede the bullet inside. All that matters to you happens before exit.

For this reason, the .24s are not ideal for elk hunting. In open country at moderate ranges with good presentations, strong 6mm bullets can be deadly. But in the catch-as-catch-can of elk hunting in elk cover, they fail. You need never cripple an elk, no matter what cartridge you use, if you limit your shots to those sure to kill. The trouble with the 6mms is that they require you to pass up shots you could easily make with heavier bullets.

Thinking back on the last ten big game animals I've shot, including four elk, I'd have fired a .243 or 6mm or .240 Weatherby at only seven. Now, killing is not always necessary, but passing would have come hard on the six-point bull shoulder-shot in heavy cover with a .338 or the big mule deer buck anchored, going away, with a .35 Whelen.

If you are willing to forego the thickets and the long-range shots where bullet expansion is either too violent or inadequate, if you're willing to shoot only when you can shoot precisely and at elk standing the way you want them, the 6mms will work. Here are some loads from people who have hunted a lot with the little sixes. First, the .243:

An Alaskan hunter uses 100-grain Nosier Partition bullets, 43 grains IMR 4350 for bears and caribou. A shooter from the Midwest relies on 100-grain spitzers of unspecified make and a stiff load of 48 grains H-4831. An eastern deer load that can be used for elk is 37 grains IMR 4320 pushing a 105-grain Speer bullet. Writer Ken Waters has used that bullet with 43.5 grains IMR 4831, recommending as well the 100-grain Sierra with 44.5 grains IMR 4831. That charge can also be used with Winchester's ball powders, 780 BR and 785, behind 100-grain bullets. Most of these loads will chronograph about 3,000 fps. Another load worth trying would be 46 grains Accurate Arms 3100 with Nosler's 95-grain Partition bullet, for 3,100 fps.

As with the .243, any medium-burning powder will work in the 6mm Remington: H-414, H-335 and H380; IMR 4895, 4320, 4064: Hercules Reloder No. 12, 15; Norma 203, 204; Accurate Arms 2520; Winchester 760. The heaviest bullets, though, usually work best with slower powders: IMR or Hodgdon 4350 and 4831, Hercules RL 19, Accurate Arms 3100, Norma 205. With 100-grain bullets, try 46.5 grains IMR 4831 or Accurate Arms 3100, 45 grains IMR 4350, 47 grains Norma 205 or Winchester 780 BR or 785. Velocities should exceed 3,000 fps.

While the .243 Winchester at 300 yards just matches the muscle of the .25-35 at 100, Weatherby's .240 delivers much more punch. At 300 yards, its 100-grain bullet has dropped only 5 inches from a 200-yard zero and retains 1,660 foot-pounds. The big case calls for slow powders: IMR 4350, 4831, 7828; Hodgdon's H-4350, H-4831, H-450; Accurate Arms 3100, 8700; Hercules RL 19 and 22; Winchester 780-BR and 785; Norma 205. Some medium-burning powders work well, though -- notably Winchester's 760 and Hodgdon's H-414. Try 48 grains 760 or 49 H-414 to give 100-grain bullets 3,150 fps. With 52 grains of Accurate Arms 3100 or Hodgdon H-450 or H-4831, or 49.5 grains IMR-4350, you should approach 3,250. Author’s note: now, 20 years after this manuscript was published, powder options for both cartridges have multiplied!

Some tests have shown the .240 Weatherby to group tighter with 75- to 90-grain bullets, like many .243 and .244 rifles. But if there's a cartridge made for 24-caliber big game bullets, the Weatherby is it. Hundred-grain bullets by Nosler, Sierra and Hornady, Speer 105s and Nosler's 95-grain Partition are the best you can buy for big game in 6mm. Now Barnes and Swift offer controlled-expansion bullets for the sixes, as do Hornady and Norma, Remington and Winchester.

Weatherby's .240 generates extra bullet-opening velocity to significantly extend effective range on rib-cage shots. Close up, it may be no better than the Winchester or Remington rounds, as higher velocity puts more strain on the bullet, promoting fragmentation. Velocity translates to energy on paper, but retained bullet weight, not velocity, is crucial at short range. The little sixes have no bullet weight or diameter to spare. Upset must be controlled, without undue fragmentation.

On a shelf above me is a little piece of cardboard with a 3/4" cluster of .243 bullet holes. It was fun to shoot that group, fun always to shoot a rifle that funnels bullets to the same spot, spitting them with soft recoil and a thin, almost apologetic report. In contrast, big-bore elk cartridges that thrust their payloads downrange with a boom and the jab of a flying piece of sewer pipe don’t appeal to me. Still, when I can't pick the shot and I must shoot the elk, those delightful, accurate -- and versatile -- 6mms stay in the rack.