Five years after the .244 Rem. became the 6 mm Rem., the inevitable happened: Roy Weatherby introduced an even more powerful .24 cal. In those naïve days a magnum had to have a belted case, or it wasn’t really a magnum. (This was long before modern shooters discovered that a brass belt was as senseless as suspenders on a kangaroo.) So Roy devised a sort of belted .30-’06 Sprg. case, complete with the double-radius Weatherby shoulder, and there stood the .240 Wby. Mag.

The .240 Wby. Mag.’s case is about long as a .30-’06 Sprg. case and has the same diameter rim, but the belt reduces case capacity. In my measurements of fired brass, the .240 Wby. Mag. holds about 5 fewer grains of propellant than the .25-’06 Rem. So no, the .240 is not a belted 6 mm-’06.

Today there are five factory loads, ranging from an 87-grain soft-point at 3,523 fps to a pair of 100-grain loads at 3,411 fps. These loads are chronographed in a 26-inch barrel, which used to be the standard Weatherby factory barrel length. However, today the Weatherby website lists only .240s with 24-inch barrels, though no doubt a 26 inch could be ordered from the Custom Shop.

For the past three years my wife, Eileen, and I have been shooting a Weatherby Ultra Lightweight Mark V in .240 Wby. Mag., and in this rifle the 100-grain Nosler Partition factory load chronographs around 3,300 fps. This is still quite respectable, and the factory ammunition is very accurate, with three-shot groups at 100 yards. averaging 0.60 inches, center to center. The load has taken a number of mule deer.

The fastest 100-grain, .25-’06 Rem. handloading data in any current manual comes from Alliant: 52.6 grains of Reloder 22 for 3,400 fps. There is no way the .240—with 8 percent less propellant space, and pushing a skinnier bullet—can match that velocity from a standard 24-inch barrel. This claim is supported by the same handloading manuals.

There’s nothing wrong with a 100-grain bullet at 3,300 fps, but today we have several “premium” 6 mm bullets weighing 85 to 95 grains. These easily reach the 3,400 fps range, and despite not weighing the traditional 100 grains, they will take big game handily.

A couple years ago Eileen field-tested the then-new 90-grain Nosler E-Tip. We received a sample box of bullets in early autumn, and I quickly worked up some loads. Ramshot Magnum propellant worked best, grouping three shots into around ¾ inches at 100 yards at 3,375 fps. The first field test was on a doe pronghorn at 311 yards., according to a Leica rangefinder. It stood quartering toward us, and the first shot broke the big shoulder joint. The doe staggered but didn’t go down, so Eileen put another bullet through the ribs broadside, and that was that. Both bullets exited, but the penetration of the first bullet was most impressive, because of the bone encountered on an angled shot. This load also shoots very flatly: When sighted in 2-inch high at 100 yards, the E-Tip lands only 2-inches below the point of aim at 300 yards.

The 85-grain Barnes Triple-Shock X-Bullet, 85-grain Nosler Partition, 90-grain Swift Sirocco II, and 95-grain Nosler Partition will also work fine on lighter big game in the .240 Wby. Mag. In the 6 mm Rem., any of the heavier conventional bullets will also do the job, but there’s also no harm in using a premium bullet, especially if hunting northern deer or even bigger game. This is heresy to many hunters, but I know quite a few people who have killed caribou, elk and even polar bears with 6 mm rifles, usually with one shot.

What about the 50-year-old concept of the 6 mms as varmint rounds? Today probably 98 percent of .243 Wins., 6 mm Rems. and (especially) .240 Wby. Mags. are strictly used on big game. A few .243s and 6 mms do show up on prairie dog towns, but these are normally heavy-barreled specialty rifles, not the light sporters Warren Page promoted. The reason? Most shooters have found that a light 6 mm is not only a pain in the shoulder after a couple hundred rounds, but also loud. This doesn’t mean much to our well-protected ears, but the report often drives prairie dogs underground quickly. It would also take an affluent prairie dogger to put together a collection of 1,000 rounds of .240 Wby. Mag. brass.

Another factor is that when modern, plastic-tipped varmint bullets are combined with riflescopes with multi-point reticles, the range of smaller varmint rounds is greatly extended. A .223 Rem. is a viable 500-yard prairie dog cartridge today, a distance that used to belong to larger cartridges. Thus the real role of the 6 mms today is mostly on larger varmints, from ’chucks up to coyotes. According to some of my Canadian and Alaskan friends, 6 mms are also apparently fine wolf rifles.

With the popularity of the .243 Win. there’s really no reason for the 6 mm Rem.—except that it’s such a well-designed cartridge. The .240 Wby. Mag. has noticeably more zip than either the .243 or 6 mm, yet recoil is still so mild that almost anybody can shoot one well, even in a rifle like the Weatherby Ultra Lightweight Mark V, which weighs about 6 pounds, 8 ounces with a typical 3-9X scope. With modern bullets, it turns out that either of the “other 6 mms” is also a great cartridge for our larger varmints and smaller big game, too.