February 21, 2020
The most prolific creator of wildcat cartridges was P.O. Ackley. During the 1940s and ’50s, he developed an extensive portfolio that became widely known as Ackley Improved (AI) wildcats. Ackley’s signature features included a less tapered case and an abrupt 40-degree shoulder angle, both to increase case capacity. He also developed several belted “short” magnums based on the .300 H&H case.
One key feature of the AI chamber is that it maintains the same headspace as the parent case. That means factory ammo can be safely and reliably fired in a rifle chambered for an AI cartridge.
During the nearly 50 years I’ve enjoyed handloading, I’ve experimented with several wildcats, including a few of Ackley’s, such as the .257 AI and the .280 AI. My latest foray into experimenting with a wildcat round came about accidentally. I had ordered a set of dies, some ammunition, and component bullets to prepare a report on handloading the .300 PRC cartridge for the 2020 edition of the Hodgdon Annual Manual. When I ordered the dies, someone who handled my order mistyped the part number, and I received a brand-new set of .30-06 Ackley Improved dies instead.
I decided to keep the dies and convert my .30-06 Savage Model 110 rifle to .30-06 AI. That way I could build some handloads and compare their performance to that of several .30-06 handloads I had developed and fired in that rifle for past columns.
With the reloading dies and the rechambered rifle in hand, I embarked on this project. It was straightforward, and it produced some interesting results.
The accompanying chart lists the results for the .30-06 hunting handload I developed previously with Sierra’s 180-grain Spitzer and 57.5 grains of Alliant’s Reloder 19 powder, plus the ballistic data I obtained with five .30-06 AI handloads. Fireforming was accomplished without mishap. I annealed the once-fired brass before fireforming and didn’t lose a single case.
Because of the greater capacity (approximately 3 grains, or 5 percent), I could safely start with the 57.5-grain powder charge and work up from there. I bumped the charge weights up in one- or half-grain steps and fired two, five-shot groups with each load. The 60.5-grain load gained 130 fps, and accuracy hovered around one MOA. The rifle’s pointblank range increased by approximately 25 yards.
I measured the velocity eight feet from the gun’s muzzle with an Oehler chronograph, and I used the usual pressure indicators of primer appearance and bolt lift to estimate how safe the “hotter” handload recipes were. They were safe in my gun. Coincidentally, the Speer Reloading Manual #4 (circa 1960) includes recipes for the .30-06 AI, and the maximum velocity listed exactly matches my results.