The .30-06 Ackley Improved
By Chuck Hawks
P.O. Ackley is perhaps the most famous of all wildcatters. There are probably more cartridges named for him than for Remington. Although, offhand, I can't think of many that achieved commercial status.
One of the more common, and also controversial, of the Ackley cartridges is the .30-06 Improved, which was developed around 1944. The .30-06 Ackley Improved is based on a .30-06 case fire-formed in an Ackley Improved chamber. This means that, in a pinch, the owner of a .30-06 Ackley Improved rifle can shoot standard .30-06 factory loads, although the bullet will usually shoot to a different spot than Ackley Improved loads.
Anyway, the result is a "blown out" case with minimum body taper and a sharp 40 degree shoulder angle. This increases case capacity and, with maximum loads, velocity. The case length remains 2.494" and the maximum overall cartridge length is 3.350". Bullet diameter is still .308"
Fans of the cartridge say that the .30-06 Improved nearly equals .300 Magnum velocities, while detractors say that it barely surpasses the standard .30-06 in performance--and then at the cost of a custom rifle and custom ammunition that cannot be purchased commercially. Oddly, both arguments have some validity.
The traditional British load for the .300 Belted Rimless Magnum (.300 H&H) drove a 150 grain bullet at a MV of 3000 fps and a 180 grain bullet at a MV of 2750 fps. That is because the .300 H&H was not factory loaded to maximum pressure. The .30-06 Ackley can indeed equal or exceed these velocities with modern powders. (The .30-06 Improved cannot equal a .300 H&H loaded to maximum permissible pressure with modern powders, but that is another story.)
And it is also true that if the .30-06 Improved is compared to the standard .30-06 with top factory loads (such as the Hornady Light Magnums), the Improved cartridge shows little or no advantage. The Hornady Light Magnum .30-06 offering with a 150 grain bullet claims a MV of 3100 fps, and with a 165 grain bullet the MV is 3015 fps. These velocities equal those that can be obtained by a reloader using maximum loads of canister powders at the same pressure in a .30-06 Improved rifle.
So I guess it depends on how you look at the .30-06 Improved. Is the glass half full or half empty? Most savvy reloaders do not load to maximum pressure in any case, so the Improved cartridge's performance advantage may be a moot issue.
The fifth edition of the Nosler Reloading Guide shows that with 150-180 grain bullets the .30-06 Improved has a MV advantage of about 100 fps over the standard .30-06. With a 180 grain Nosler bullet, 57.0 grains of AA3100 powder gave a MV of 2685 fps, while 61.0 grains of the same powder gave the same bullet a MV of 2890 fps.
AA3100 powder gave the best accuracy with 180 grain bullets in the Nosler tests, which used reformed Winchester cases and Win. WLR primers in a 24" Lilja test barrel with a 1-10" twist.
Copyright 2005, 2012 by Chuck Hawks. All rights reserved.