By Chuck Hawks
The 6mm-284 is one of the few wildcat cartridges to become more popular than its parent cartridge. When the .284 Winchester was introduced, wildcatters had a field day necking it up and down. .243" diameter bullets proved to be a good choice for long range shooting, and today I understand that reloading dies in 6mm-284 outsell dies for the regular .284 Winchester. Evidently the 6mm-284 fills a need.
It relates to the 6mm-06 as the .284 Winchester relates to the .280 Remington. If you are pining for a custom 6mm rifle with greater performance than the 6mm Remington and it is a short action rifle that is to be the basis for your conversion, the 6mm-284 may be for you.
Like all wildcats, there is no official SAAMI pressure limit for the 6mm-284, nor is there a set cartridge overall length. In this situation, the chambers of custom rifles can and do vary, which affects pressure and velocity. It is one of the inconveniences of owning a wildcat.
What will happen to the 6mm-284 if the .284 Winchester is discontinued and .284 brass becomes unavailable? This is always a problem for the rare popular wildcat based on an unpopular parent case. But perhaps before that occurs Winchester (or someone) will adopt the 6mm-284 as a factory cartridge.
Producing a 6mm-284 case is simply a matter of running .284 Winchester brass through a 6mm-284 forming die. Trim to a length of 2.155". Naturally, the 6mm-284 is at its best with slow burning powders. These are necessary to achieve the high velocities of which the cartridge is capable, and to keep pressures within reason.
With 75-85 grain bullets the 6mm-284 makes an awesome varmint cartridge, similar to the .240 Weatherby. The Hodgdon Data Manual 26 shows that 51.0 grains of H4831 can drive an 80 grain varmint bullet to a MV of 3397 fps; 55.0 grains of H4831 delivers a MV of 3683 fps with the same bullet.
Like the .240 Weatherby, the muzzle blast and report are a problem for most varmint shooters, not to mention the accelerated barrel erosion if the shooting gets fast and furious. As varmint cartridges, the .243 Winchester or 6mm Remington are better choices.
The 6mm-284 is at its best with the heaviest bullets in the caliber, those weighing 90 grains and up. The 100 grain and 105 grain spitzer bullets are a particularly good choice for medium size big game at long range.
According to the Hodgdon Data Manual 26 the popular 100 grain spitzer bullets can be driven to muzzle velocities of 3011 fps with 46.0 grains of H4831. 49.0 grains of the same powder gives a 100 grain bullet a MV of 3207 fps.
Unlike many reloading manuals, the Hodgdon Data Manual gives pressure information for many loads. In the case of the H4831 maximum load for the 100 grain bullet at 3207 fps the pressure listed was 49,100 cup.
At 3200 fps the muzzle energy of a 100 grain bullet is 2274 ft. lbs. At 200 yards Hornady's figures for their 100 grain Spire Point bullet are 2651 fps and 1561 ft. lbs. The trajectory of that bullet at a MV of 3200 fps looks like this: +2.5" at 100 yards, +3" at 150 yards, +2.4" at 200 yards, and -3" at 305 yards.
Note: An article about the 6mm-06 and 6mm-284 can be found on the Wildcat Cartridge Page.
Copyright 2005 by Chuck Hawks. All rights reserved.