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>> Dies For The Ackley Improved Cartridges :: By J. Marshall Stanton on 2002-06-04
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Before the proliferation of factory belted magnum cartridges, a devout and steady following of the Ackley Improved cartridges persisted during the 1950’s and into the early to mid 1960’s. Parker O. Ackley, while certainly not the first of cartridge wildcatters to “improve” a standard cartridge, brought a standardization of these modifications to the firearms industry.

Typically, the Ackley Improved concept involves straightening out the cartridge to minimum body taper, and putting a sharp shoulder on the case while leaving the neck at standard length. The increase in powder capacity varies from one cartridge to another, but can be from 3% to as high as 9% depending upon the factory cartridge being “improved”. Part of the genius behind these modified cartridges is the ability to shoot standard dimension factory rounds in the firearm, as well as the “improved” version. Too, simply firing loaded rounds of the parent case in the improved chamber easily forms brass without the need of specialized case forming dies.

In addition to the obvious advantages of increased case capacity, and thus the propensity for increased velocity potential, are other benefits not immediately apparent. One of these attributes is a significant reduction in rearward thrust against the bolt or breech-block of the rifle. This reduces strain on the firearm by means of the minimum body taper of the chamber and case, thus reducing to some extent the amount of rearward thrust, since the case more tightly grips the relatively straight chamber.

The second of these benefits is the fact that typical brass stretch of a fired case is significantly reduced as a direct result of the minimum body taper. This reduction in brass stretching not only minimizes required case trimming, but drastically improves case life, especially in those instances where the parent case has pronounced cartridge taper, such as in the .22 Hornet, .30-30 Winchester, .303 British, .30-40 Krag and .375 H&H. In such cartridges as these, case life is astonishingly improved.

Now, for the primary incentive for which most firearms are rechambered to the “improved” versions of various cartridges is the increase in performance. While in some cartridges such as the .270 Winchester, the actual yield is rather negligible, those cartridges that have the most body taper benefit proportionately better according to the increase in case capacity. Those same chamberings that benefit the most in terms of case stretch, also display the greatest velocity gains due to the significant increase in case capacity by straightening out their pronounced body taper.

While the increase in velocity is very real, and in some instances quite significant, the majority of claims regarding increased velocity are greatly exaggerated. Too, it’s apparent when looking over old loading manuals listing the “improved” cartridges, that the comparisons weren’t made comparing apples to apples. By this I mean that the pressures to which the improved versions were loaded, were much higher than those to which the standard SAAMI round were pushed. For instance, the .30-06 Springfield, when loaded to SAAMI specifications of 50,000 C.U.P., yields about 2,700 fps. when loaded with a 180 grain jacketed bullet. However, if you look at older loading data for the .30-06 Ackley Improved, you’ll see that same 180 grain jacketed bullet running out the bore of a 24” barrel at something just over 3.000 fps! The gain appears very substantial, until you also realize that the Ackley Improved version is also loaded to somewhat over 65,000 psi. This apparent gain comes with the price of increased pressure, plain and simple. In looking at some modern loading data for the .30-06 Springfield when loaded to its pressure potential in modern guns and new brass, such as found in the Barnes Reloading Manual Number Two, we find the 180 grain bullet pushed along to something over 2,800 fps with no less than six different powder combinations. So, looking at the old ’06 loaded to modern pressures, and comparing it to the “improved” version, while there is a difference, it isn’t nearly as dramatic as it might appear at first glance when comparing to loads at lower pressure standards.

It all comes down to simple math. You just can’t take a 3% increase in powder capacity, and turn that into a 10% velocity gain without turning up the pressure of the cartridge! However, there are cartridges such as the .30-30, .375 H&H, 30-40 Krag, .303 British and .22 Hornet that perform like thoroughbreds once given the Ackley Improvements. In these cases, the velocity gains are real, and of substantial increase, while working within the parameters of normal pressures, simply due to their more efficient form and increased capacity. Of course, as mentioned earlier in this article, these cases share the common trait of having radical case taper in their factory guise. All this is said, simply to make the reader aware that all claims regarding velocity gains aren’t as they might at first appear, and before making the plunge for the improved version, some research, and unbiased evaluation can be very revealing.

Now, as we look at the possible pros and cons of improving a cartridge, the factors of consideration don’t begin and end with velocity and case life. One must also look at resale value of the firearm if you ever decide to sell the gun; the market value is most generally slightly lower for an “improved” chamber gun, than one of SAAMI specs also they are more difficult to sell. Also there is the issue of reloading dies, as these can be very expensive to obtain, and in many cases are special order numbers with price tags reflecting that status.

Dies are the focus of this article, in the fact that not all, in fact very few of the Ackley Improved cartridges actually mandate a set of AI custom dies. In fact, most all of these modified cases can be loaded with a little ingenuity and resourcefulness using off-the-shelf dies!

In most instances, the Ackley Improved cartridges are found in turn-bolt rifles, and a few lever actions. This being the case, neck sizing of the brass is all that is necessary to obtain proper functioning in the firearm, and thus, full-length specialized Ackley dies may be avoided entirely.

Over the years, I’ve had occasion to own several Ackley Improved chambered guns, load for them and evaluate their performance. Too, being the frugal sort of individual that I am, I’m loathe to spend eighty bucks on a set of dies unless it’s an absolute necessity. So, mother necessity steps in, and American ingenuity takes over. A few of those improvisations are outlined below to help spark the imagination.


The .223 Ackley Improved holds true to the standard :improved” form, retaining its original neck length and featuring minimum body taper and a 40 degree shoulder angle. While wild claims regarding velocities have been published for this ‘improved’ cartridge, the simple math shows a 5% increase in case capacity, and of course that equates to about 2% increase in actual velocity gains with equal pressures. However, it does have exceptional case life and is very forgiving in load development.

Reloading of the .223AI may be accomplished by utilizing a neck sizing die, such as the excellent Hornady New Dimension Neck Sizing die. Simply adjust the die so that it sizes the neck within about 0.050” of the shoulder. Then seat bullets using a seating die that doesn’t “form fit” the case, such as the Hornady New Dimension Bullet Seating die, or the Lee Precision bullet seating die, as both of these dies have floating bullet seating stems, and don’t contact the shoulder of the cartridge case when seating bullets.


The .30-30 Ackley Improved cartridge deviates from the normal Ackley design in the fact that the shoulder is moved forward when compared to the parent cartridge. This is easily accomplished since the .30-30 headspaces on its rim, rather than the shoulder, thus fire-forming this case is no object. However, you can’t use standard .30-30 dies for neck sizing, due to the forward shoulder position and the steep shoulder angle, when coupled with the minimum body taper of the cartridge. In this case, once again a neck sizing die such as the Hornady .30 Caliber Neck Sizing die, which is not cartridge specific, but rather designated by bore diameter works beautifully. As in the previous example, simply adjust the die to size all but the last 0.050” of the neck, and then use either the Hornady New Dimension or Lee Precision bullet seating dies with their floating bullet seating stems. The combination of these dies works superbly, and surely beats the cost of custom dies.

Loading for the Ackley ’06 is no different than the previous two examples, simply employ a Hornady .30 Caliber Neck sizing die for sizing, and either the Hornady New Dimension or Lee Precision bullet seating dies with their floating bullet seating stem for bullet seating. Size the case necks in the same fashion as the previous examples.

The beautiful thing about neck sizing dies that are caliber specific rather than cartridge specific, is that they may be used for so many different cartridges. For instance, the Hornady .30 Caliber Neck Sizing Die pictured is used to load the .30-30 Ackley Improved, .30-40 Krag Ackley Improved, and .30-06 Ackley Improved. A similar .35 caliber neck sizing die loads .35 Remington Ackley Improved, .35-30 Ackley Improved, .35 Whelen Ackley Improved and .358 Norma.

You might wonder why I specify sizing the neck to within 0.050” of the shoulder. The reason is this: I discovered long ago, that the unsized portion of the neck serves two purposes, one it keeps you from inadvertently sizing too far and setting the shoulder back, and secondly it helps center the cartridge case in the chamber by being full diameter to start with, thus somewhat enhancing accuracy of your loaded ammo.


Something that I discovered quite by accident, was that the Lee Precision Collet Dies Sets, the dies that utilize a collet assembly to press the case neck against a mandrel to accomplish resizing, will work perfectly on all Ackley Improved cartridges that employ the same case-neck length as the parent cartridge. These dies never contact the shoulder region of the brass, and only size the neck. Interestingly, I’ve had superb accuracy results in the AI cartridges when using these dies. They work for all the Ackley Improved cartridges tested, with these exceptions: .30-30 AI, .32 Spcl AI, .303 Brit AI, .30-40 Krag AI, and variations on these cases. If you have a standard Ackley Improved Cartridge these Collet Dies from Lee are a very cost effective alternative to specialty dies.


An example of this is with the .375 H&H Ackley Improved. As can be seen in the photograph, this improved version of the factory case uses the same length neck, and as such, is an ideal candidate for using the Lee Collet Dies. Not only can the collet die be used for case sizing, but the seating die included with the set is adequate for bullet seating in the AI version as well. Try getting a set of .375 H&H Ackley Improved dies anywhere for under the thirty dollar cost of the Lee dies!

Interesting too, when using these collet dies on the .375 H&H AI, I checked the seated bullet run-out with and RCBS Case Master gauging tool. The cases were sized with the Collet Sizing die, trimmed to uniform length, necks step expanded with a custom “M” type sizing die punch made by Mike Gibony, and the bullet seated using the Lee bullet seating die that came in the die set. The bullet was Beartooth Bullets’ .377”-270g SPGC. The average total bullet run-out with a twenty round sampling was 0.002” This type of consistent concentricity is consistent with the finest bench-rest type performance standards. Accuracy of the loads? They shoot into about ¾” at 100 yards off of a sandbag benchrest using a 4x scope.

Another good sizing option for the Ackley Improved cartridges is Redding’s Neck sizing die system that employs various diameter titanium nitride bushing inserts. This system allows varying the neck tension on your loads, by changing the bushing used, and can be a great boon to those using cast bullets in their Ackley Improved cartridges.

The bottom line is this. Although the custom specialty dies may be nice to have, they are far from a necessity, and excellent quality ammo, of superb accuracy may be assembled using somewhat unorthodox and creative resourcefulness, employing dies that may already be sitting on your reloading bench. Lastly, for the shooter earnestly considering having his rifle rechambered to one of the Ackley Improved cartridges, the high cost of reloading dies don’t have to be a serious consideration, as demonstrated in this article.
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