These days it is fashionable to speak about niches in the marketplace. There are automotive niches, and housing niches, and clothing niches, and (for all I know) quiche niches. There are niches in rifle cartridges as well, and one of the most interesting is the trio of very powerful cartridges that are meant for the biggest North American game and much of what you hunt in Africa. Far more potent than any 7mm or .30-caliber magnum, they are also much longer-ranged and milder kicking than really big rounds like the .416 and the .458. All essentially .338 caliber, they offer a unique combination of truly significant wallop, long-range capability, and manageable (by many people but not everybody) recoil.

THE .338 WINCHESTER MAGNUM This supremely useful cartridge was introduced in 1958 as one of a family of three cartridges, including the .264 Winchester Magnum (long faded into oblivion), and the .458 Winchester Magnum (which has found huge popularity in Africa). Although you can get .338 loads with bullets as light as 200 grains, the proper bullet weight for the cartridge is 250 grains. It moves out at 2600 fps (note that all velocities given here are from my own chronographing, not factory figures). The only other bullet I'd consider is the 230-grain Fail Safe slug made by Winchester. It will penetrate just as well, and it goes about 100 fps faster.

A .338 gets by very nicely with a 22-inch barrel, which is short and handy. However, it kicks, and hard. A .30/06 produces about 15 foot-pounds of recoil, but a .338 doubles that. If you have a .338 that weighs much less than 9 pounds, you will have to put a muzzle brake on it or the Legendary Chicken Fairy will come out and dance before your eyes when you shoot it.

THE .340 WEATHERBY MAGNUM This one dates from 1962 and is the .338 in spades: a longer cartridge that holds a lot more powder and gives 250-grain bullets between 200 and 300 fps more velocity at the muzzle than the .338 Winchester. It doesn't kill anything any faster, but it makes hitting at long range-past 300 yards-a lot easier.

Weatherby loads the .340 with bullets ranging from 200 grains to 250, but trust me, you want to stick to the 250s, and for two very good reasons: First, the long, heavy 250-grain bullets lose velocity very slowly, and they are still traveling at great speed even when they get out past 300 yards. Second, a 200-grain bullet moving at .340 velocities (3200 fps) is like a rocket-propelled grenade. You don't want to do that kind of damage to an animal you intend to eat.

Weatherby makes its .340 rifles with 26-inch barrels, but you don't need that length. A 24-inch tube will do fine. My own .340 is made by New Ultra Light Arms, has a 24-inch barrel, and gives me over 2800 fps at the muzzle with 250-grain bullets. It weighs 81/2 pounds, which is about a pound less than you want it to weigh, but when Melvin Forbes built the rifle, I told him I was willing to gain portability at the expense of getting my brains scrambled, since they were pretty well addled already.

.338 REMINGTON ULTRA MAG Introduced in 2002, the .338 RUM is also the largest of the three. It delivers, on paper at least, 25 percent more muzzle energy than the .338 Winchester. (Note: If you are distraught at the chart's seeming contradiction in the .340's numbers versus those of the .338 RUM, the explanation is that the former is operating at high pressure, while the latter is loafing along with a mild handload.) It is part of a family of four Ultra Mag cartridges-the others being 7mm, .300, and .375-which is Remington's bid to have the biggest and fiercest magnums on the block.

Remington wisely loads the .338 only with 250-grain bullets-the Remington Core-Lokt and the incomparable Swift A-Frame. It holds slightly more powder than the .340 Weatherby and kicks a bit harder, which is plenty hard.

Like Weatherby, Remington equips their .338 RUM rifles with 26-inch barrels in order to get every last foot per second from those huge charges of slow-burning powder. However, I will always trade off a few feet per second for a handier rifle, and I had my .338 RUM barrel cut back to 231/2 inches. Theoretically, this should have cost me lots of muzzle velocity, but in reality I lost only 38 fps and accuracy increased markedly.

The Remington Model 700 LSS (laminated stock, all stainless steel) that I have weighs 91/2 pounds with scope aboard. It's no pleasure to shoot, but it's not crippling, either. Do you need cartridges that are this powerful? Not for deer, but if you hunt elk or big bears on this continent, they are invaluable. They may be niche cartridges, but it's a big niche.