Ackley’s Favorite Son

by Fred Zeglin

Practical & Versatile, Factory ammo, longer brass life, and some were better than others.

270 AI vs 280 AI

Like all gunsmiths P.O. Ackley developed strong opinions about what cartridges had value during his fifty plus years building guns. Unlike most gunsmiths, Ackley based his opinions more on experimentation and empirical evidence rather than on feelings or judgments based on unverified information. Few gunsmiths have the broad experience that Ackley brought to the table, he was a barrel maker, reamer maker, cartridge designer, experimenter, tool maker, reloading expert, understood engineering principals, was knowledgeable about metallurgy, and was a gunsmith.

Parker Ackley (he hated to be called Parker, his friends called him P.O.) started gunsmithing part-time during the depression of the 1930’s while he ran the family farm full time. In 1936 he decided to sell off the farm and start gunsmithing full-time. This was likely a decision influenced by the depression, even today when the economy slows down gunsmiths know that business will pick up in repair because folks find it more cost effective to fix an old gun than to buy a new one. The Ackley family farm was near Granville in northern New York State, this part of the country was a Mecca for wildcatting and benchrest shooting in the 1930s and 40s.

The author with his son Dewain (Z-Hat Customs Inc.) in front of the “chicken coop’–Ackley’s old gunsmithing shop.

Purchasing a small gun shop in Roseburg Oregon was Ackley’s first full-time foray into the gunsmithing business. He bought the store from Ross C. King a man that Ackley apparently respected; he called Ross, “one of the old time gunsmiths on the west coast.” During that first year his family operated the business and got settled in Roseburg while Ackley apprenticed as a barrel maker for the better part of a year. Upon arriving in Roseburg he immediately set about building barrel making machines and tooling. He had started designing his first wildcat while still apprenticing as a barrel maker, that was to become the .228 Ackley Magnum when finalized. In a very short period of time Ackley produced several new designs.

The important point here is that Ackley became a well known, respected barrel maker and gunsmith between 1937 when he began operating the shop in Roseburg and 1942 when he went to work for the Army Ordnance Department in World War II. During that period of about five years in Roseburg he introduced a full line of magnum wildcats that were literally the forerunners of today’s standard length magnums as well as several fire-formed improved designs. Most gunsmiths are in the business for years before they develop the confidence in their abilities and skills to take up wildcatting, if they ever do. Ackley was a wildcatter from the very beginning of his career. All these factors made him uniquely qualified to opine on cartridge performance.


P.O. Ackley was eminently practical. The concept of “Improved” cartridge design is based almost exclusively on practical benefits. Factory cartridge designs in the 1930’s and 40’s were antiquated; they still had a lot of taper and tended toward gently sloping shoulders with long necks, common to black powder cartridges. Reviewing Ackley’s designs you will notice that he became a proponent of minimum body taper and sharper shoulders from the beginning of his career these features typify the improved case design most gunnies today would identify as “Ackley Improved”.

While Ackley was well aware that shooters and reloaders were interested in maximum velocity and accuracy, he was also honest enough to tell the truth about performance when a cartridge did not produce better results than the parent cartridge. A good example of this would be the 220 Swift Ackley Improved; Ackley reported that the results ballistically showed no improvement over the standard 220 Swift, except for mechanically. When he talked about this “mechanical” benefit Ackley was referring to the ability of improved design cases to minimize case stretch, which provides longer case life, less case trimming, and fewer case head separations.

Ackley performed experiments to determine if the ‘Improved’ design really accomplished what is claimed of it. The most well known experiment utilized a 94 Winchester action, rechambered to 30-30 Ackley Improved. Ackley tested that chambering with various degrees of excessive headspace; from this experiment he reported having learned the following:

  1. The ‘Improved’ design does increase the ability of the cartridge case to grip the chamber walls.
  2. The case does carry some of the pressure.
  3. Bolt thrust is minimized.
  4. An oily chamber or case will allow the case to slip under pressure, thus increasing bolt thrust.
  5. Ackley stated that this test disproved the fallacy that certain actions had arbitrary pressure limits.

The last point about the actions ability to handle pressure is of the greatest interest to the wildcatter, or for that matter any reloader who tries to get the most velocity he can from his loads. Barrel makers will tell you that the standard barrel steels we use today, 4140 Chromoly steel and 416 Stainless have an “Ultimate Tensile Strength” of about 140,000 Pounds per Square Inch (PSI). That is the point where a catastrophic failure is likely. The “Yield Strength” is about 20% below the ultimate tensile strength, this is the point at which the steel will deform to the point that it will become unserviceable.   We know from these numbers that the barrel can probably contain more pressure than most if not all actions. Most actions will be damaged long before our loads hit the yield strength of the barrel, some much worse than others.

With that in mind here is a quote from Speer’s Wildcat Manual #2, “P.O. Ackley, however says he does not care what pressures are just so long as he does not have extraction trouble or primer leaks, and he says that the straight body facilitates extraction and prevents undue backthrust on the bolt. In that he is probably correct and more and more ballisticians are inclined to agree with him.”[1]

What Ackley was basing his opinion on is what most reloaders use as their ultimate test for any given load; how many times can I reload my brass without loose primer pockets or other signs of failure. Most reloaders figure if they get 5 or 6 reloads from a lot of brass then the load is safe in their particular gun, and they are probably right.

Reloading seemed to grow in popularity in the 1930’s at the same time that “Wildcatting” was thriving, Books like “Handloader’s Manual” by Earl Naramore, and “Complete Guide to Handloading” by Phil Sharpe came out in 1937 and 38 respectively paving the way for all the reloading manuals that have followed. Ackley even mentions one of Naramore’s latter editions in his writing as a great resource for reloaders. Once reloading became popular the idea that case life was the best measure of safe pressure was in widespread use by reloaders and wildcatters, so Ackley stands in good stead with the gunsmithing and reloading community on this issue.

Nowadays we have strain gauges and Piezo-electric transducers to tell us more clearly what our chamber pressure is. The availability of this more accurate information has caused gunsmiths, and avid reloaders to take a closer look at the chamber pressure generated by various loads. This is where “Improved” design cases seem to have held an advantage over most factory designs. Ackley argued that the straight walls of the “Improved” case allowed the chamber pressure to be directed at the barrel more, and the breech face less. Thus reducing bolt thrust, which equals strain on the action. In other words, he believed that since the barrel steel can contain the pressure safely and the bolt trust is reduced then we can safely extend the maximum pressure limit so long as the case will handle it without failure (multiple loadings being the test).


One of the much touted advantages of the Improved cartridge concept is that you can use factory ammo to fire-form brass. Often the idea that if you went on a hunt and forgot or lost your ammo you could still buy factory ammo and save the hunt. One writer called this “pure Madison Avenue” making me wonder just how much he really hunts, because over the years I have had more than one client tell me this has happened to them.   Of course they may not have had Ackley Improved guns but nonetheless they were forced to buy ammo locally in order to hunt. In fact I once flew to a hunt and to avoid problems at the airport I decided to buy ammo upon arrival. The point being that even if the odds are against ever needing to do so, at least you could in a pinch.

The biggest advantage to being able to fire factory ammo is that forming brass for these wildcats is very easy. There is no need for expensive forming dies. Anyone who has formed brass for a wildcat using dies will tell you that even if it’s fun it takes a fair amount of time and attention to detail to form brass. So, in this day and age when most shooters have limited time to devote to their hobby the time saving characteristic of fire-forming brass from factory loaded ammunition is a valuable attribute that makes such wildcats a more versatile choice for busy shooters. Once the brass is formed its a simple matter to work up loads that will utilize the added case capacity of the ‘Improved’ chamber.

How much velocity is lost when fire-forming brass in an ‘Improved’ chamber? Not as much as you might think. Depending on the cartridge in question the velocity loss during fire forming is usually between 50 and 100 feet per second. The reason for this velocity loss is simple, energy is being used up in the fire-forming process and as the volume of the case increases so pressure drops. Pressure is directly related to velocity.

Once the cases are fire-formed they can be loaded to full potential. Nearly all Ackley Improved designs deliver their best results with heavy for caliber bullets, increasing versatility in loading. There are some designs that offer greater improvement than others, simply because they increase the size of the boiler room more than average. Examples would be 25-35 Ackley Improved, 7×57 Ackley Improved, and 30-30 Ackley Improved. These three deliver far more velocity than their factory counterparts with their substantially increased case capacity. Examples of cases that do not gain a whole lot for the ‘Improved’ treatment would be the 22-250 Ackley, 25-06 Ackley, and the 270 Ackley Improved.

Two versions exist for the 280 Ackley–SAAMI and Standard Ackley

This brings up an interesting point. Ackley himself was not a big proponent of the 270 Winchester Ackley Improved. Yet he was highly vocal about recommending the 280 Ackley Improved. On the surface you might think that these two cartridges are so similar that this dichotomy makes no sense?   Lets look a little closer:

270 Winchester Ackley Improved

This cartridge did not impress Ackley; he considered it to be overbore. He used it in some of his tests to show that when cartridges are overbore it takes huge increases in powder to add small amounts of velocity. Ackley stated that the standard 270 Winchester was superior in design to the improved version. Truthfully, if you are inclined to use only the heaviest for caliber bullets with slow burning powders you may see some desirable results with the improved design.

Tests were performed by Ackley using the 270 Win. AI cartridge. He reports on this testing in Volume 1 of “Handbook for Shooters and Reloaders”, 1962. To prove that bore capacity is an issue worth considering; a barrel was first chambered for a 270/308 wildcat, maximum loads were established by working up loads until the primer was blown, one grain less powder than what it took to blow the primer was the max load for each chambering tested, insuring that we had an apple to apple comparison.

The Ackley improved 270 Winchester allowed eight (8) more grains of powder than the 270/308 wildcat, velocity was only increased 82 fps. Then the barrel was rechambered a final time to a wildcat 270 with a short neck that Ackley did not name, but it was likely a 270 Gibbs. An additional 5 grains of powder could be burned in the last cartridge with a whopping gain in velocity of 4 fps. Proving that there is a point of diminishing returns with any given bore diameter.[2]

280 Remington Ackley Improved

The 280 Remington is nothing more than an American adaptation of the 7×64 Brenneke. One could argue that it is the commercial version of the 7mm-06 wildcat. Others claim it’s just a cousin to the 270 Winchester. Ackley even points out that the 280 pretty well duplicates the venerable 285 OKH wildcat.[3] In truth Remington chose to move the shoulder forward on the 280 by about .050” in order to prevent shooters from chambering a 280 Remington in a 270 Winchester chamber. Consequently it has slightly more case capacity than the 7mm-06, about 5 grains of water weight, when you get to the 280 Ackley Improved you have 7.4 grains more capacity by water weight over the 7mm-06.   This cartridge first appeared in the 1959, “Supplement to the Handbook for Shooter and Reloaders.”

The 280 Ackley Improved can push a 175-grain bullet as fast as the 7mm Remington Magnum. Think that sounds crazy? Check published load data for the standard 280 and the 7mm; you will be surprised how close they are in performance with the 175-grain bullet. Of course with lighter bullets the Magnum probably has some advantage in velocity. So the 280 Ackley Improved can delivery magnum performance with less powder and therefore with less recoil than the magnum cartridge. On top of that, there is a following for cases without belts. That is probably why the 280 AI continues to be a popular wildcat.

So why does the 280 Ackley Improved have such an advantage over the 270 Ackley Improved? Well there are two factors that play into the disparity. First, anytime you increase bullet diameter for the same weight projectile you will increase velocity, because the powder gasses have a larger diameter to push against. Thus more energy is transferred to the bullet. Secondly, the 280 AI has 3.2 grains water weight more capacity than the 270 AI, so it’s not as level a playing field as one might think.

Knowing all that, you can see why P.O. Ackley preferred and recommended the 280 Ackley Improved over the 270. He knew how much of an advantage the 280 case had over it’s smaller cousin.

In 2006 Nosler announced that they would be offering their second limited edition rifle in 280 Ackley Improved, 500 guns were to be offered. Nosler is also offering their quality brass headstamped for this cartridge as well. Nosler is not alone in offering the 280 AI as part of their line, several small production rifle makers like Ed Brown, and Kenny Jarrett are offering rifles chambered in the 280 AI. Montana Rifleman is offering the 280 Ackley Improved in their barreled actions.   The 280 AI is very popular and most custom rifle smiths have a reamer on hand for the caliber.

Norma has not announced their plans for the 280 Ackley Improve but the author received a box of test ammo from Norma, head stamped for the 280 Ackley Improved loaded with a 140 grain Accubond Bullet.

I wonder if Ackley would be surprised the longevity of his offspring, the “Improved” cartridges?

[1] Speer Wildcat Rifle Loads, Volume 2, 1956

[2] Handbook for Shooters and Reloaders, by P.O. Ackley, 1962

[3] Handbook for Shooters and Reloaders, P.O. Ackley 1962

12 Responses to Ackley’s Favorite Son

  1. What Nosler introduced as the .280 Ackley is not truly a .280 Ackley. With a true .280 Ackley, the headspace is set .004″ shorter than the parent .280 Remington go gauge allowing a .280 Remington to be fired in the Ackley chamber to blow out the .280 to make the .280 Ackley. A .280 Remington shouldn’t be fired in a Nosler .280 Ackley chamber as Nosler lengthened the head space for the .280 Ackley when they submitted their cartridge to SAMMI standardization. SAMMI specs on the .280 Rem. headspace are 2.100″ minimum to 2.110″ maximum. Their specs for the .280 Ackley are 2.140 to 2.150″ maximum for the Nosler version of the .280 Ackley. If the Nosler .280 Ackley was truly an Ackley cartridge then the headspace would be 2.096″ and would allow you to fire form .280 Remington brass in the .280 Ackley chamber. To fire form .280 Remington brass in a Nosler .280 Ackley chamber you will get an incipient case head separation or worse an actual case head separation. If you have a Nosler .280 Ackley it is imperative to fire only Nosler brass in the chamber.

      • I read the article that you linked. There are some discrepancy’s on the chamber prints that I have and the SAAMI print, that just don’t line up. My reamer prints are Pacific Tool & Gauge prints. The measurement on the .280 Remington print from the base to the neck shoulder junction is 2.1924″. The measurement for the 2001 print for the .280 Ackley print is 2.1895. That would line up with the approximately .004 shorter headspace for the method that P.O. Ackley used when chambering for an Ackley Improved. The SAAMI print shows 2.1742″ from the base to the neck shoulder junction. Which turns out to be .0153″ shorter than the original .280 Ackley print shows for the same dimension. I know that headspace isn’t set off the neck shoulder junction. I don’t doubt his test in the above link. Pretty easy to tell. I have both Pacific go gages. The original .280 Ackley go gage with the original .280 shoulder and the newer 280 Ackley with the 40 degree shoulder on the gage. I’d actually prefer all the Ackley go gages to have the 40 degree shoulder, but most of mine don’t. If both gages are the same, it would be easy to tell when chambering a barrel. The bolt should close on both go gages the same with the same feel on how tight the bolt closes on the go gage. The discrepancy in the prints showing the SAAMI chamber to be .0153″ shorter than the original chamber is a little concerning. But, in actual practice gunsmiths don’t chamber off of SAAMI prints. They chamber off the go gages provided by the reamer manufacturer which is what he did in the article. If both go gages are the same, then so be it. That’s great. If I had a .280 Ackley in my shop right now, I’d check with both go gages.

        • The article about the 280 AI Empirical test mentioned above is based on the chamber reamer prints from Pacific Tool and Gauge for each cartridge discussed. Manufacturers often apply the tolerances allowed by SAAMI when they draw up prints. This is for ease of production of the tool.

          The introduction of 40 degree shoulder gauges for Ackley Improved cases is a relatively new thing. If you read Ackley you will see he explains the junction of neck and shoulder method of headspacing in Volume 1, pages 154-156.

          Modern Datum lines are specified as a diameter along the angled shoulder. Datum line on the 280 Ackley SAAMI is at the .375″ diameter along the shoulder. The length called out for this gauge is 2.140″, which appears to be .014″ shorter than the Traditional design.

          On the Traditional 280 Ackley drawing we end up with a headspace length of 2.1542″ . I measured this length on my cutaway chamber and guess what, that is the length to the junction of the neck and shoulder. Thus headspace matches the drawings correctly.

          What we have is two different methods of measurement. However they achieve the exact same result. It’s just a math problem.

          • Fred,there are some screwy things going on with these chamber prints that don’t add up. There are two measurements from the SAMMI print to the original .280 Ackley print that can’t be right. The SAMMI print from the base of the chamber to the neck shoulder junction is 2.1742″ My 2001 chamber print is 2.1895 at that same point. This whole thing may be moot as the reamer makers may have hashed all this out as evidenced by both your original go gage and your new SAMMI go gage headspacing the same exact chamber.

            Here are links to the chamber prints that I am referencing.

            The (S)dimension from bolt face to neck shoulder junction is 2.1924″.

            That same (S) dimension would be 2.1895″. That would be .0029″ shorter than the .280 Remington at that same point would align fairly closely to the go gage being .004″ shorter for the Improved cartridges headspace referenced on page 155 of Ackley’s Vol I Handbook for Shooter’s and Reloaders.


            The measurement from the bolt face to the neck shoulder junction on the SAMMI print shows to be 2.1742″.

            The corresponding headspace measurements at the .375″ diameter on each of the three prints show to be 2.100″ for the .280 Rem., 2.1542 for the 2001 print .280 Ackley and 2.1400″ for the SAMMI print. The 2001 .280 Ackley print has a longer length measurement for the .375″ shoulder datum line showing than is shown for the .280 Remington print at that same point. That shows that the print is measuring off a 40 degree shoulder and not off the 17 degree 15′ shoulder of the parent .280 Remington. Probably the best way to find out what was decided on this would be to talk to Dave Kiff and find out what it is. As it’s pretty obvious that the problems with the measurements have been worked out. I’m not the only one that had a problem with the SAMMI dimensions from their print. Wade Hull at Shilen, Inc. shared with me his same concerns about these prints a few years ago at the NBRSA Nationals.

          • I understand your concerns. That’s why I used chamber prints from the reamer maker and did the test with the gauges in hand.

            As you said, the reamer makers have parsed this out and all is well. If you buy an Ackley go gauge either Tradition or SAAMI you will get the same headspace, it’s just the location of the gauging in the chamber that varies.

            All the best!

          • Fred, I made a chamber gage that is made with the .280 Ackley reamer run in far enough to cut the shoulder on a piece of barrel stub and then cut it off square on the other end. Dropped them over the shoulder end of each go gage that I have and measured from the top of the chamber gage to the bottom of the go gage with a set of calipers. Both the 2001 and the 2012 made go gages measured identically. Interestingly enough they were both .004″ shorter than the .280 Remington go gage which is what they should have been. The newest one isn’t marked as being SAMMI, but is what it was supposed to be when I ordered it. That mirrors the same exact thing that you found. Evidently the reamer makers and Nosler worked out the discrepancy between the prints.

            I was looking for some Nosler .280 Ackley brass at Midway and found an interesting description pertaining to a set of Redding Master Hunter dies in .280 Ackley Improved as follows:

            The SAAMI spec cartridge carries the approved name of 280 Ackley Improved. The older wildcat has several names including 280 Ackley Improved 40°, 280 Rem Improved 40°, 280 Imp 40°, 280 Ackley, 280 Rem Imp, and more. The SAAMI spec 280 Ackley Improved chamber is 0.014 inches shorter at the datum line headspace dimension than the traditionally accepted wildcat chamber spec as previously produced. These dies are for chambers that are cut to the SAAMI specification and are stamped 280 Ackley Imp. Any Redding dies made before 2011 are stamped 280 Rem Imp 40° and are built to the originally accepted wildcat specs. These older dies will not bump the shoulder of cases for a SAAMI chamber. In other words, the old dies are too deep for the current SAAMI chamber. Redding makes a Competition shellholder that is 0.014 deeper than the standard #1 shellholder so the owner of a wildcat chamber can use the current SAAMI spec dies for safe resizing. Failing to use this shellholder or to back the die away from a standard shellholder by a minimum of 0.014″ will result in too much shoulder bump which may create an unsafe, excessive headspace condition when fired in a traditionally dimensioned wildcat chamber.

            There certainly is plenty of confusion pertaining to the new Nosler .280 Ackley Improved SAMMI standard. It looks like it’s going to take years for all this to get straightened out and reach everyone involved.

            My chamber gage showed the exact same thing that your test did in that both gages measured the same in use.

  2. Very interesting as I had a 284 necked up to 338 and find what P.O. Ackley say’s is oh so true. A Nosler 200 grain ballistic tip at an honost 2800 fps. 338 magnum uses 68 grains to reach 2829 fps. My 338/284 uses 58 grains of the same powder for 28 fps less velocity. Extremely accurate, much less recoil. Thanks for the read, again, very interesting.

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