What Are "Ackley Improved" Cartridges and Should You Use One this Season?

Have you ever wanted to squeeze just a little more velocity out of your hunting rig? You like your rifle and the cartridge it shoots, and you don’t want to make a big change. But adding 150 feet-per-second of bullet velocity would increase your effective range and make you more comfortable taking that shot across the canyon.

You aren’t alone. Legendary wildcatter P.O. Ackley had a similar impulse when he pioneered the “Ackley Improved” (AI) family of wildcat cartridges. Rather than invent an entirely new cartridge, Ackley took an existing case and fired it in a rifle with an Ackley Improved chamber. This modified (or “improved”) the cartridge case in a way that increased muzzle velocity and performance.

It sounds like a no-brainer and an instant commercial success. But Ackley invented dozens of these Improved variants, and only the .280 Ackley Improved has made the jump from the reloading bench to the ammunition factory, courtesy of Nosler.

AI cartridges are perhaps the most popular wildcat cartridge designs, but the fact that only one has been widely(ish) adopted begs the question: are they worth it? Keep reading, and you can decide for yourself.

From left to right: .280 Rem vs. .280 AI; .30-30 AI vs. .30-30 Win; .243 AI vs. .243 Win.

How Do You Make an Ackley Improved Cartridge?

Ackley Improved cartridges have been so popular among everyday hunters because you can make them yourself. If you have a rifle chambered in an Ackley Improved cartridge, you can fire the standard version of that cartridge in that rifle to create fire-formed cases with the correct dimensions.

For example, if you like the .30-30 Win. but want better muzzle velocity, you can purchase a rifle chambered in .30-30 AI. Then, you can fire your standard .30-30 Win. loads in your new rifle to create .30-30 AI cases. Those cases can be reloaded with .30-30 AI dies, andvoila!—you have a .30-30 that hits 2,600 fps, a 200 fps improvement over the standard cartridge.

HowAI cartridges increase bullet velocity is a testament to P.O. Ackley’s genius. He realized that increasing the angle of the shoulder on a bottleneck rifle cartridge–usually to either 28 or 40 degrees–increases case capacity and, therefore, potential bullet velocity.

At least, that’s the layman’s explanation. The actual physics has been outlined by P.O. Ackley's biographer and accomplished wildcatter, Fred Zeglin. He explains in “Cartridge of the World” that, technically speaking, a wider shoulder diameter is what explains the velocity gains. This wider shoulder lowers the ratio between the case capacity with the bullet seated and the total capacity of the bore and chamber, what he calls the “expansion ratio.”

“When we ‘Improve’ a cartridge, we create more chamber volume for the same bore volume, so the expansion ratio is less,” he writes. “This seems confusing until you realize the pressure curve for any load is a curve, with a peak pressure and a timeline. So, we’re talking about changing the timing related to the pressure. The greater the pressure at the muzzle when the bullet exits, the higher the velocity.”

Whatever the reason, the proof is in the pudding. AI versions of standard cartridges increase bullet velocity. Sometimes it’s only three or four percent; sometimes it’s greater. But the improvement is there, which explains why AI cartridges have been attracting hunters and sport shooters for nigh on 70 years.

Data from Fred Zeglin, “Cartridges of the World”

Should You Get One?

Of course, if you want a more powerful hunting cartridge, you can always just get a new rifle chambered in something a little hotter. This, I think, is why AI cartridges haven’t been more commercially successful: you can’t shoot an AI cartridge in a gun chambered for the standard version. Instead, you have to buy an entirely new rifle, and if you have to do that anyway, a lot of hunters figure they might as well jump to a magnum cartridge or something with significantly better performance. Plus, since the .280 AI is the only Improved variant available from the factory, you’ll probably have to reload all your own ammunition.

Ackley aficionados will counter that once you have that AI-powered rifle (so to speak), you can fire both standard and Improved versions of the cartridge. This gives you the flexibility to take advantage of Improved performance while also using standard loads if you don’t have time to dedicate to the reloading bench. Improved variants also offer better performance without delivering the recoil of a magnum cartridge, which is always a big plus.

I can see both sides of this argument. If you roll your own ammunition, you’re tickled by the idea of fire-forming your own cartridges, and you just generally like tinkering with guns and ammo, the Ackley Improved concept is for you. It’s a great way to dive a little deeper into the Wonderful World of Firearms, and the performance gains are real (though they also sometimes come with shorter barrel life).

But if your only reason to get an Ackley Improved rifle is for 150 more fps of bullet velocity, save yourself some time and money and just get a gun chambered in a different cartridge. As Icovered here, modern versions of older cartridges often offer better downrange performance, and you can also step up to a magnum class if you want to chase a bigger critter.

Last Shot

Whether you like the idea of giving your favorite hunting cartridge the Ackley treatment or think the whole concept is a relic of a bygone era, you can’t deny that P.O. Ackley had a profound impact on ammunition development. His steeper shoulder angles are a hallmark of modern cartridges, and his constant striving for better, more effective ammunition has inspired many to undertake the same project. Perhaps more importantly, Ackley gave everyday hunters what we’re always looking for: an exciting, rewarding way to give ourselves an edge in the field.

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