The 7mm Dakota
By Chuck Hawks
Dakota Arms offers a line of proprietary magnum hunting cartridges designed by Don Allen and based on the .404 Jeffery case shortened to function in standard (.30-06) length actions. These come in a variety of calibers including 7mm. Factory loaded ammunition is supplied only by Dakota.
The 7mm Dakota uses standard .284" diameter bullets. It is based on a rimless, bottleneck case with a rim diameter of .545". This case is 2.50" long and has a sharp 30-degree shoulder. The cartridge overall length is 3.33".
Because the 7mm Dakota has a larger rim diameter than the standard belted magnum cartridges, it requires a bolt specially manufactured or modified to match. No doubt this will continue to limit the cartridge's popularity.
7mm Dakota factory loads are offered with a 140 grain and two 160 grain bullets. Dakota also offers unfired 7mm brass to reloaders, priced at $175/100 cases.
The 140 grain bullet has an advertised muzzle velocity (MV) of 3400 fps and muzzle energy (ME) of 3593 ft. lbs. The 160 grain bullets have an advertised MV of 3200 fps and ME of 3637 ft. lbs.
The handloader has many more bullet choices, of course. Projectiles from 100 to 175 grains are commonly available, but for a case the size of the 7mm Dakota the 139-140, 150-160 and 175 grain bullets probably make the most sense. Slow burning powders work best with these bullets in the 7mm Dakota.
The Sixth Edition of the Hornady Handbook of Cartridge Reloading shows 7mm Dakota loads for their various 154 grain bullets at MV's from 2700 fps to 3200 fps with a number of powders. IMR 7828 seems like a reasonable choice for the 7mm Dakota. 66.7 grains of IMR 7828 behind a 154 grain Hornady Spire Point Interlock bullet gives a MV of 2700 fps. A maximum charge of 76.7 grains of the same powder gives a MV of 3200 fps and a ME of 3501 ft. lbs. with the 154 grain bullet.
The trajectory of that load looks like this: +2.4" at 100 yards, +3" at 150 yards, +2.4" at 200 yards, +0.7" at 250 yards, -2.1" at 300 yards, and -6.3" at 350 yards. The MPBR (+/- 3") of that load is 311 yards. These Hornady loads used Dakota cases and Federal 215 primers and were chronographed in the 25" barrel of a Dakota 76 rifle.
Note: A full length article about the 7mm Dakota Magnum can be found on the Rifle Cartridge Page.
Copyright 2005 by Chuck Hawks. All rights reserved.