The 6mm Remington started life in 1955, the same year as the .243 Winchester. It was originally named the .244 Remington.

It is based on the rimless .257 Roberts case necked down to accept .243 inch bullets, and with a sharper 26 degree shoulder. Rim diameter is .473 inch, case length is 2.233 inches, and the maximum overall cartridge length is 2.825 inches. The SAAMI maximum average pressure is 52,000 cup.

The .244/6mm Remington will cycle through most short action rifles, whether bolt, lever, pump, or semi-auto. It is fine choice for hunters who intend to shoot varmints, predators, and deer size game with the same rifle. Recoil energy is low, about 10 ft. lbs. for most loads, and trajectory is flat, both of which contribute to the 6mm's reputation for outstanding accuracy.

Ballistically, the 6mm Rem. with a 100 grain bullet is nearly identical to the popular .270 Win. with a 130 grain bullet. It has much less muzzle blast and recoil than the .270, and shoots just as flat with a bullet of the same sectional density. How could it not be a run away success?

But unfortunately Remington viewed their new .24 as primarily a varmint cartridge, and they rifled the barrels of their factory rifles with a 1-in-12 twist. This meant that the heaviest spitzer bullet the .244 would stabilize at long range weighed 90 grains. Remington factory loads for their new caliber featured a 75 grain varmint bullet and a 90 grain bullet for light to medium game. Winchester .243 rifles came with a 1-in-10 twist, which would stabilize spitzer bullets as heavy as 105 grains to very long range. Winchester factory loads for their new cartridge offered an 80 grain varmint bullet and a 100 grain big game bullet. A lot of .24 buyers were looking for a flat shooting deer rifle without much recoil, and a 100 grain bullet seemed more impressive than a 90 grain bullet. By 1958 Remington realized that they had made a mistake, and changed the rifling in their .244 barrels to 1 turn in 9 inches, but it was too late.

In other words, Remington misread the market, and Winchester got it right the first time. Sales of the .244 Remington languished while .243 Winchester sales soared. It probably didn't help that the .243 Winchester was introduced in the sexy Model 70 Featherweight rifle, while the .244 Remington was introduced in the plain and rather clunky Model 722.

Sales were so poor that in 1963 Remington discontinued the .244, and then reintroduced the exact same cartridge with a new name: the 6mm Remington! Only this time the barrels had a 1-in-9 twist, and the factory loads featured 80 grain varmint and 100 grain big game bullets. And the new 6mm cartridge was introduced in the new Model 700 rifle, one of the sharpest bolt actions that ever came down the pike. Remington's excellent but misunderstood cartridge was finally on the right track.

The .244 and 6mm cartridges are completely interchangable, and anyone with a .244 rifle can shoot 6mm ammunition in complete safety (or vice-versa). Remington .244 rifles made from 1958 on can stabilize all 6mm bullets, while those made in 1955 through 1957 are limited to loads using spitzer bullets not heavier than 90 grains for best accuracy.

Generally, in 6mm, the 70 to 80 grain bullets are the varmint bullets; the 90 to 105 grain bullets are designed for larger game, and the 85-87 grain bullets can be either (but not both). For comparison, the Speer 80 grain spitzer has a ballistic coeficient (BC) of .365 and a sectional density (SD) of .194; the Speer 100 grain big game spitzer bullet has a BC of .351, and a SD of .242. These are good numbers, superior to the numbers for the same bullet weights in .25 caliber.

When using any of the .24's to hunt medium size big game animals, bullet selection is very important. The varmint bullets will not give adequate penetration and must be avoided. On the other hand, rapid (but controlled) expansion is very important, as the small diameter 6mm bullet has little shocking power if it does not expand and expend its energy inside of the animal.

Because the necked down .257 case has a bit more capacity than the necked down .308 case, the 6mm requires a tad more powder to achieve the same velocity as the .243 Winchester. However, when both are loaded to the maximum, the 6mm has a modest velocity advantage.

Factory loads in 6mm call for an 80 grain bullet at 3,470 fps, and a 100 grain bullet at 3,100 fps. The heaviest bullet factory loaded for the caliber, the 105 grain Speer spitzer (with a BC of .443 and a SD of .254), is factory loaded to 3,060 fps. This is 140 fps faster than the .243 factory load with the same bullet.

Remington's 100 grain PSP Core-Lokt bullet is factory loaded to a MV of 3,100 fps. Sighted to hit 2.5 inches high at 100 yards it will strike about 3 inches high at 150 yards, 2.2 inches high at 200 yards, and 3 inches low at 296 yards. At 200 yards this bullet has 1,470 ft. lbs. of remaining energy, and 1,207 ft. lbs. at 300 yards. With this load so zeroed the 6mm Rem. is about a 300 yard antelope and deer cartridge.

The 6mm is an excellent cartridge to reload. According to the Nosler Reloading Guide No.5 their 80 grain Ballistic Tip varmint bullet can be driven to a MV of 3179 fps in front of 38.0 grains of IMR 4064 powder; 42.0 grains of IMR 4064 raises the MV to 3451 fps. The popular 95-100 grain bullets can be driven at a MV of 2856 fps in front of 42.0 grains of RL19 powder, or 3159 fps with 46.0 grains of RL19. The folks at Nosler used Remington cases and Federal 210M primers for their load development. The loads were chronographed in a 24 inch barrel.

I understand that the 6mm has been a steady seller since its reintroduction, and all of the "Big 3" loading companies now offer 6mm Rem. factory loads. Serious reloaders tend to prefer it, and it is reputed to be a very flexible cartridge for which to develop loads. The 6mm Remington offers outstanding ballistic performance in a standard short action cartridge.