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22-250 Ackley Improved

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One of a long list of cartridge designs improved by Parker Otto (P. O.) Ackley, chiefly through the 1950s, the 22-250 Ackley Improved duplicates 220 Swift capacity and performance. Depending on which cases are used, either one might have slightly greater capacity. The difference is meaningless and any load combination safe in one, is safe in the other. These will give indistinguishable results.

Ackley’s design was genius. He reduced case-body taper to about 0.001-inch per 0.1-inch length, which works perfectly to allow easy extraction, even with loads generating very high pressure. Once the camming action of the bolt has withdrawn the case as far as it will, the case is free of the chamber. Ackley incorporated a sharper, 40-degree, shoulder.

Factory ammo would chamber in the AI gun with solid headspace control. The case first engages the chamber at the junction of the shoulder and neck. Then the case shoulder and body flex to allow easy and full chambering; on rimless-bottlenecked cases that headspace on the shoulder, this technique prevented case stretching when the round fired.


On rimmed cases, he often reduced neck length when doing so was possible without shortening the neck too much.

The problem was, gunsmiths refused to bother to read and follow the chambering instructions Ackley included with his reamer designs. With bottlenecked rimless designs, to correctly rechamber a barrel from the original chambering to the AI version, it is necessary to remove the barrel from the gun, move the shoulder forward enough to allow the barrel to screw into the action one additional turn and then shorten the barrel shank the same amount.

With rare exception, so-called gunsmiths were wont to do this. They ruined an endless stream of guns by simply running the AI reamer into the unaltered barrel. As such, cases stretched significantly and dies correctly made to size AI cases drove the shoulder back so far case life was extremely limited.

Because of this, the AI concept got a bad and entirely undeserved reputation. The bad reputation belonged to the so-called gunsmiths who had a shingle, a nail, and a Colt 45 Revolver to use as a hammer to drive in the nail so they could hang their shingle.

The AI design is just about perfect and it is a shame it was tarnished by wanna-be backyard hacks.

Generally, the AI designs are superior in all ways when chambered correctly. However, I must add one note of caution: Ackley and others of the era were dangerously lax when it came to respecting the value of proof-testing.

Many of them recommended and published loads of that era generated pressure exceeding Proof-Load Pressure. Refer to the 22-250 and the 257 AI discussions to understand the catastrophic events to which that approach can lead.

Heritage of this case dates to the 1870s with the introduction of the 40-70 Ballard case.


The text associated with the cartridge description reflects opinions and conclusions of the author, M.L. (Mic) McPherson. Lee Precision and its employees do not necessarily either agree or disagree with any of his comments. We present these with due deference to his recognized expertise in the firearms field. His acumen extends to handloading and all aspects of ballistics - internal, external, and terminal.
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