November 07, 2023
During the decade after World War II, gunsmith P.O. Ackley pioneered the “improved” cartridge case. Steepening the shoulder angle and fire-forming most of the taper out of a cartridge case’s body increases internal capacity. With more room for gunpowder, handloaders achieve significantly greater velocities. Plus, since the datum point at the shoulder/neck juncture is maintained, parent versions of the cartridge in question may safely be fired in the improved chamber.
Best known of the myriad cartridges Ackley modified—from the .22 Ackley Hornet to the .475 Ackley Mag.—is the .280 Ackley Improved, so we’ll use it for discussion in this article and to spotlight the characteristics of improved cases, as applied to handloading.
The .280 Ackley was submitted to SAAMI by Nosler in 2008, so it’s a legitimate factory cartridge now. Its claim to fame is that it achieves 7mm Rem. Mag. performance with substantially less powder, less recoil and less barrel wear while providing more magazine capacity.
For the handloader, one of the most significant benefits is that improved cartridge cases exhibit far less case stretch when fired. This is primarily due to the very steep shoulder. In most cases, the angle is 40 degrees from the axis of the cartridge. For reference, compare that to 17.5 degrees on the .30-06, 25 degrees on the .300 Win. Mag., and a scant 8.5 degrees on the long, tapered .300 H&H case.
When gunpowder ignites, it causes brass to flow forward. The gentler the angle of the shoulder, and the more taper in the case in general, the more easily brass flows. Cases with abrupt shoulder angles like improved rounds resist this flowing-brass phenomenon, and they will last longer and have better integrity throughout their lifespans.
Better integrity means there’s less chance of case head separations, split necks and other case failures. In the past 12 years I’ve probably handloaded more .280 Ackley cartridges than all others put together, and I have yet to experience a single case head separation or split neck. Meanwhile, I’ve had cases fatigue and fail in several other chamberings, from the 6mm Creedmoor to the .338 Rem. Ultra Mag.
This minimal stretch also means less trimming to proper case length. I don’t know about you, but I’ve always considered case trimming an evil that’s barely justified by necessity. Not my favorite pastime.
Another advantage of an improved case is less easy to quantify and dips into internal theoretical ballistics: Propellant in improved cases is believed to combust more evenly and more efficiently.
Let’s use a couple of examples on extreme ends of the spectrum to paint a mental visual of why. On the improved end, let’s stick with the .280 Ackley. On the non-improved case design end, let’s go with the .300 H&H—one of my all-time favorites.
The H&H features a long, tapered case and a mild shoulder angle. As a result, propellant granules are free to flow down the bore in the wake of the departing projectile, combusting as they go and continuing to create propellant gases.
This following action occurs in all cartridge cases, to one extent or another. However, the .280 Ackley and other improved case shapes provide an abrupt wall on the forward end of the propellant chamber. This holds the column of gunpowder inside the case a bit more effectively as the primer shoots flame through the powder, and the bullet begins its journey down the barrel.
As a cohesive powder stack rather than a blizzard of loose granules tornadoing off down the bore, the propellant ignites more evenly and burns more completely. In theory and in practice, improved cartridge cases tend to provide smaller extreme spreads and tighter standard deviations in velocity.
There’s one more benefit of improved cases, and that’s more consistent headspacing. Long, sloping shoulders on standard cases have a less predictable, less consistent shape to lock up against. As a result, it’s harder to achieve handloads with that minimal-but-reliable, exactly right amount of headspacing when your bolt goes into battery. Improved cases have abrupt shoulders with crisp angles. This makes it easier for the handloader to set the sizing die to just kiss the shoulder and optimize minimum, consistent cartridge headspacing in the chamber.
However, life isn’t all roses when handloading improved cartridges. Traditionally, there’s the slightly tedious task of fire-forming cases. Generally, this is done by shooting factory ammo or handloaded parent cartridges in the improved chamber—for example, .280 Rem. cartridges in a .280 Ackley chamber. Bang, out comes a perfectly shaped improved cartridge case.
Cool, you bet. However, this task requires time, expensive ammo and/or components and has the dubious side effect of applying barrel wear. But here it’s worth pointing out that correctly shaped and properly headstamped cases are available for some of the improved-type cartridges these days, eliminating this task.
Next on the list of downsides is the fact that sharp-shouldered cartridges with minimal body taper tend to feed less smoothly than traditional cartridges, which have gentle shoulders and plenty of body taper. Usually, this isn’t a significant issue, but be aware that occasionally it takes an action-tuning job by a savvy gunsmith to make your Ackley cartridges feed like butter.
Last, reloading data is sparse and scarce for most improved cartridges. Only the .280 Ackley is common enough to be found in most handloading manuals. P.O. Ackley published data for most of his modified cartridges in his Handbook for Shooters and Reloaders, but it should be used with caution. He used bulk military surplus powders, and today’s iterations may or may not have precisely the same burn characteristics. Plus, Ackley tended to be rather enthusiastic in his pursuit of speed.
In the final analysis, improved cartridge cases provide elevated performance for handloaders but at the expense of increased effort. That’s nothing new. Handloading is at its core an intensive pursuit of performance—effort, time and cost be durned.