In a post we wrote a couple of years ago but that never appeared on this blog (because it was never finished), we wrote about legendary 20th Century riflesmith and cartridge wildcatter Parker Otto Ackley, known to all as P.O. Ackley.

PO Ackley made an entire career of making what he called “improved” cartridges. Each of the Ackley improved cartridges was based on some mainstream cartridge but with an increased powder capacity and a sharper shoulder, which implies less taper in the body of the cartridge itself.

We described Ackley similarly in another post that did get published, in 2012. That of course understates Ackley’s career, because apart from all his cartridge wizardry, Ackley was a gunsmith, barrel maker, and a writer with a prodigious capacity for work.

in a new book by Fred Zeglin, this career is explored and evaluated, and Zeglin actually emulates some of Ackley’s famous experiments, including these on Bolt Thrust that are excerpted at

Since the post-WWII years, if not before, there has been an ongoing argument concerning whether breech thrust (bolt thrust) is reduced by the improved case design. P.O. Ackley has certainly influenced the argument. The definition of an improved case is pretty simple. The case body is blown out to minimum body taper, which is described by Ackley as 0.0075 per inch taper. Shoulder angles between 28 and 45 degrees are normally considered to be improved, although it could be argued that any shoulder sharper than the original parent case is improved. Finally, an improved design allows the firing of a factory cartridge in order to fireform the brass for the new design.

…a method of recording breech trust was necessary in order to go beyond the somewhat subjective experiments that P.O. Ackley wrote about in Handbook for Shooters and Reloaders Vol. I. There Ackley used a Model 94 Winchester because, as he stated, “We often hear that the Winchester Model 1894 action was designed for low pressures and is an action which could be described as ‘weak.’” The purpose of his experiment with the ‘94 was to prove that the improved case design minimized bolt thrust; that the brass will support and contain some pressure; that oily chambers increase bolt thrust; and finally, the notion that actions are designed for specific pressure ranges is a fallacy.

Zeglin conducted a high-tech version of Ackley’s tests, using a test fixture he developed, “a .30 caliber barrel with a universal breech plug to allow for adjustable headspace, and to accommodate the strain gauge utilized by the Pressure Trace.” He developed loads beyond the SAAMI pressure limit for the .30-30 Improved, and discovered that even with excess headspace, the Improved case stayed in place, extruding the primer instead of shearing its head off. Conclusions:

[W]as Ackley right about his findings?

Yes, but he may have missed a point or two.

Since .30-30 brass is thick and pressures are low relative to brass strength and case capacity, with most appropriate powders pressure is not a big problem. To be fair, we did find some powders that will develop pressure far beyond SAAMI levels for the .30-30 AI case. Because the brass is so thick, it actually cannot stretch and cause head separations due to excess headspace. In that respect the .30-30 is not a good choice for Ackley to prove that improved designs handle pressure better.

However, Ackley used the .30-30 because the ‘94 Winchester action had been labeled weak. In this respect, Ackley did prove that the ‘94 can handle anything the .30-30 or .30-30 AI can dish out, without any question.

Bear in mind that the action of the Winchester ’94 was labeled weak by Winchester, who wanted to upsell customers to stronger rifles, like the ’95, which could handle the big-game and service cartridges of the early 20th Century with no problems.

There’s quite bit more to it, so Read The Whole Thing™. In other things in the book there is something that made us order it: Ackley’s own, previously unpublished, description of his own home-made cut rifling machine. (See the Table of Contents left).

Like any highly specialized book, it’s expensive, and has potential to go out of print at some time in the future. That’s just life in specialty book markets.

How expensive? The list price for hardcover or eBook is $60, although at this writing Gun Digest is sweetening the deal with $10 off the hardcover edition, and free shipping. (Pity they don’t offer a deal on both. We prefer hardcover books, but you can take a Kindle or iPad into the shop without worrying about getting cutting fluid on an irreplaceable heirloom). For what it’s worth, we just ordered the hardcover.

While this book rates the full price (to us at least), Gun Digest publishing does find itself overstocked from time to time, and if you’re into gun books and willing to let price be your guide, they have Under $30 and Under $15 pages, too. Free shipping if you can run the tab to $50 — we bet you can. (Dunno what the shipping is to those of you dwelling in foreign lands).

This entry was posted in Book and Film Reviews, Consumer Alert!, GunTech, Rifles and Carbines on by Hognose.

About Hognose

Former Special Forces 11B2S, later 18B, weapons man. (Also served in intelligence and operations jobs in SF).

17 thoughts on “Walking in PO Ackley’s Footsteps


I had a lovely Parker-Hale Mauser action rifle chambered in .243 Winchester back in the 80s. I had it improved, and honestly I don’t think it made much difference to the game I shot with it that the projectiles hit them at a couple of hundred fps faster than a standard .243. I never load my ammo super hot, so extraction and general functioning wasn’t any different either.

Improving may well be useful where the cartridge needs it, but for a powerful and versatile round like the .243 I think I would’ve been better off spending the money on ammo.

Dyspeptic Gunsmith

Your experience is now pretty typical of the AI cartridges with modern powders. The increase in powder capacity of the cases is, in most cases, rather modest. With modern powders, these modest improvements in case capacity results in relatively small increases in muzzle velocity, compared to those seen with older powders.

John M.


It’s always struck me that Ackley’s “improvements” were a solution in search of a problem, but that may be because I’m a relatively young guy and am uninformed on how much improvement could have been expected in the old days. What was the typical spread between a vanilla round and an AI round using older powders?

-John M.

Dyspeptic Gunsmith

Today they are, yes.

In the past, there were gains afforded by the AI cartridges, and because PO was a pretty sharp gunsmith, he did it in ways that re-used quite a bit of gunsmith’s original tooling on these rounds, and you got improvements without having to dump your original barrel.

Before modern powders, PO’s improvements were worth chasing, in some calibers. eg, the .280 Rem AI was just short of the performance of a 7mm Rem Mag – and with today’s powders, the difference between the two is now negligible.

the .243WCF is my personal favorite round. It is so versatile, accurate and pleasant to shoot. I have never went at any point in my life without at least 3.

The AI rounds had more use back in the day, anyway they certainly are not really that great for casual hunters and no handloader/wildcatters. I think a lot of people don’t understand what they are getting into and think they are getting something like a magnum round in improvement, I’m not talking about you or anything, I assume most readers of this blog are advanced enough to understand what they are doing in this respect. But the more general population


***the .243WCF is my personal favorite round. It is so versatile, accurate and pleasant to shoot. I have never went at any point in my life without at least 3.***

You are far from the only one who felt that way about the .243. Back when Glenn Nelson still ran the small arms repair facility and the match rifle shop in Warehouse A at NWSC Crane around 1976, the Navy was still running 7,62 NATO Match M1 Garands, and a few were rebarrelled to .243 to see if they could be made to work as well at 600 yards as they did at 200 and 300. The SEALS were experimenting with M14s in .243 to see if the torque from the rifling could be used to offset the up-and-to-the-right pull of the guns on full-auto. It worked well enough they wanted some .243 barrels made for their shorty-chopped down M60 mgs as well. They also built up some heavy barrelled Remington 700s in .243 that eventually went to the British SAS as *soft rifles* that became forerunners of the Navy M84 short action sniper rifles, neither a Marine M40A1 nor an Army M24 so far as features went.

Glenn had several .243 hunting and target rifles of his own and knew how accurate and useful the cartridge could be, one reason he saw it as a possible answer for some special militry purposes.



Jesse Bogan

I have a Stevens 44 1/2 single shot that was built by my old man when he was a young man. It is chambered in 218 Bee AI When we were going through dads stuff I found some correspondence between PO Ackley and my father. I can’t prove Ackley did any work on it, but it is kind of interesting to me anyway.

indeed it is.

and you mention another of my all time favorite rounds, the 218 Bee. Much better than the ore popular hornet in my opinion. better in every way. I never bothered to AI the Bee though. case life is already short on the bee. and I like it for what it is . which is a helluca lot more than the newsrand gun rag “experts” give it credit for or would even bother to test for themselves


Biggest thing I noticed while messing with improved cartridges is less need for case trimming.

I’ve only messed with 2 and don’t really consider them worth the hassle. It was fun learning about the process though.

One (30 Gibbs) was actually a wildcat and the other is the 257 Roberts AI.

Dyspeptic Gunsmith

PO’s other big contribution to guns and gunsmithing was the formation of the first formal trade school program of gunsmithing.

After WWII, returning vets from WWII asked the town fathers of Trinidad, CO, to set up some sort of gunsmithing/weapons program at the local community college. The town fathers of Trinidad approached Ackley (at that time, he has his own shop down in Cimarron, NM) and asked him to set a gunsmithing program at TSJC. The story I got whilst I was at Trinidad was that they town fathers offered him a building in Trinidad for his shop if he’d move to Trinidad.

The program opened in 1947, and has been going ever since. It’s the oldest/first formal program in gunsmithing today.

Whilst at Trinidad, Ackley engaged in a number of [in]famous experiments with guns as well as starting some of the modern ideas about sporterizing military rifles that gradually grew into the Custom Gunmakers’ Guild notions of what a high-end custom rifle should look like.

John Distai

Trinidad is also known as the place where they make Heshes. (pronounced ‘hee shees’)

Hognose Post author

Funny you should mention that. Coming in tomorrow’s When Guns Are Outlawed at 1400.

ETA — I suppose that’s a completely different kind of ‘gunsmithing’. I always thought they went to Thailand, actually. Or Denmark.

Dyspeptic Gunsmith

It was, but the MD who used to perform these operations has moved to San Francisco, last I knew.

Thanks for the heads up on this Book Hognose. I will by buying it later today.

anyone serious about firearms history should have a cop y of PO’s handbooks and Hatcher’s notebook

I have a .17 Ackley Bee round, I have kept for years. I can email you a picture of it if you care to see it

Ray in KY

OEMs do it now. Look at the popularity the 6.5mm-250 Savage AI. Or, as some refer to it, the 6.5 Creedmoor. Also about anybody’s “short magnum”. Out with the old, in with the new old.

Ray in KY

” Look at the popularity OF the ” etc. Sorry.