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Pumping up the .223: experiments with a self-loading .223 Ackley Improved.

With all the new cartridges appearing in recent years, it's curious that the selection of .22 centerfire cartridges seems to be declining. Such once famous wildcats as the .219 Donaldson Wasp and 2R Lovell, and such good factory rounds as the .222 Rem. Mag., .225 Win, and .224 Weatherby are dead or dying.

Others, such as the .22 Hornet, .222 Rem. and .220 Swift have loyal followings, but their glory days are past. What's the reason for all this, at a time when interest in varmint hunting and varmint rifles is higher than ever? Two reasons -- the .223 Rem. and the .22-250 Rem, cartridges.

Changing Varmint Scene

The .223 has the huge advantage of cheap, high quality military surplus ammunition and brass. It is accurate, light recoiling, easy on barrels, and inexpensive to reload. Its ballistics are more than adequate for the ranges and size of game most often encountered. Need more velocity and power for flatter trajectory and bigger targets? The .22-250 fills the gap.

Many varminters are coming to recognize the virtues of AR-type rifles. The best modern ARs are capable of astonishing accuracy, better than all but the best bolt-action rifles.

They also have the advantage of an immediately available follow up shot. The shooter can observe the bullet strike through the scope and if it is a little off the mark, immediately correct and fire again.

Most ARs are available in .223 only, and the design of the action and the magazine limit caliber choice to cartridges of similar length. For those wanting more power, the obvious answer is a wildcat based on the .223 case. One of the best and most popular choices is the .223 Ackley Improved.

Enhanced Performance

To "improve" a cartridge means to reshape it to increase its capacity. This can include reducing body taper, sharpening the shoulder angle, and (sometimes) moving the shoulder forward and reducing neck length. Improving cartridges was especially popular in the post-WW II era.

The easiest way to get formed cases for an improved chamber is by fireforming. Cartridge brass is pliable stuff. When a factory round is fired in an improved chamber, gas pressure blows it out to conform to the new chamber dimensions. The problem is to maintain proper headspace.

With rimmed cases, the rim keeps the case from moving forward at the blow of the firing pin. Similarly, the belt on belted magnum cases maintains headspace. That's one reason why wildcats based on the belted H&H magnum case became so popular.

With rimless cases, which headspace on the shoulder, it's not so simple. If you want to fire standard .223 ammunition with its 23-degree shoulder in an Improved chamber with a 40-degree shoulder, chamber dimensions have to be such that the factory round is a tight "crush" fit. This is the only means of ensuring correct headspace. Just running a reamer into a standard chamber generally won't do it.

Here's what P.O. Ackley himself said:

"The chamber can be reamed out so that the new chamber just barely cleans up the corner between the shoulder and neck, but this will not produce a crush fit which is necessary for fireforming factory ammunition. So the headspace has to be about .004 inch under minimum go gauge... it is almost always necessary to turn the barrel in a little bit in order to minimize headspace."

Guns & Ammo, December 1971

Ackley improved just about every case he could get his mitts on, including rimmed and belted cases. I don't believe the term "Ackley Improved" was ever copyrighted or trademarked, but when today's shooters speak of an Ackley Improved rimless cartridge, it is generally understood to mean a case with minimum body taper, a sharp shoulder (usually 40 degrees), and a chamber that will accept and fire the standard factory cartridge.

The Custom AR Arrives

In the late 1980s, practical shooting competition was expanding from handguns to include rifle and shotgun matches. I noticed several top shooters using AR-type rifles with upper units built by Lee Mosher, owner of Insight Shooting Systems Inc. (ISSI), located at Pueblo, Colo.

I shipped Mosher an AR upper to which he fitted his match package. This included a 20-inch, heavy free-floating match barrel and steel handguard with a very attractive and comfortable polyurethane cover.

Mosher converted the receiver to "flat top" configuration with a machined scope mounting rail, cut the chamber to minimum dimensions, adjusted headspace, and fitted and tuned it for accuracy and reliability.

To say the accuracy of the ISSI unit came as a shock is putting it mildly. With just a 1.5-4.5x Weaver scope, heavy factory trigger, and various brands of factory and surplus ammunition, the ISSI unit never fired one five-shot group that exceeded an inch. With a higher-powered scope, 1/2-inch groups were routine. I wrote about this unit in the November 1990 issue of GUNS Magazine.

Out Of The Blue

I hadn't talked to Mosher in over a decade, though I'd see his systems being used at matches and knew he was quietly going about his business. So it was a pleasant surprise when Mosher called in late 2001, and an even more pleasant surprise to find he was also interested in the .223 AI cartridge. He was kind enough to let me test one of his prototypes, the second .223 AI he had ever built.

Mosher built the unit around a 26-inch match-grade, stainless steel Hart barrel with a 1:12-inch twist. He fitted his machined scope rail, a chrome bolt and carrier, one-piece gas ring and titanium firing pin.

He used a JGS precision reamer to cut the chamber to correct dimensions so that factory .223 ammunition can be fired. Quality of workmanship is outstanding. The unit exhibited excellent fit, finish, and function.

The ISSI upper fit beautifully on a Les Baer lower receiver, chosen for its high quality and for the great 27-ounce Jewell two-stage trigger it carries. Fit was rock solid, with no perceptible play between the two components. I used Burns Zee rings to fit a 3.5-10x Weaver Grand Slam scope.

First order of business was to fireform some cases, which was also an opportunity to check accuracy with standard .223 ammunition and compare velocities from the 26-inch barrel to those from a standard 223 with 20-inch barrel, (See chart above).

Both types of Black Hills ammunition printed five-shot groups right around 3/4 inch in the ISSI unit. Improving a chamber generally reduces the velocity of factory ammunition slightly, due to the larger combustion chamber, but the longer barrel more than made up the difference.

Superior Quality Dies

Mosher included a set of Redding Competition dies. These dies are simply superb quality. Both sizing and seating dies use a sliding sleeve that keeps the case straight and supported. The sizing die, with interchangeable bushings, gives complete control of how much and how far the case neck is resized.

The seating die has a micrometer-adjustable dial calibrated in .001-inch increments. The first round loaded was slightly too long to fit the magazine. I measured the overall length with a dial caliper, turned the knob on the Redding die down .005 inch and ran the round through again. Checking with the caliper revealed overall length was reduced precisely .005 inch. Imagine that!

Bullet and powder manufacturers provide load data for cartridges whose case dimensions, capacity and pressure limits have been standardized. In North America the standards are maintained by the Sporting Arms and Ammunition Manufacturers Institute (SAAMI).

Companies that stamp, for example, ".270 Winchester" on cartridges, rifles, or loading dies are guaranteeing their product falls within tolerance limits for that cartridge as specified by SAAMI.

For obvious safety reasons we can't provide load data that has not been pressure tested and found to be within industry limits. Since wildcat cartridges by definition have not been standardized, there are no industry standards. Different versions of "improved" cartridges can vary significantly in such dimensions as shoulder angle, neck length, and capacity.

Thirteen Percent Increase

Even standard cartridge cases can vary in capacity due to differences in brass thickness. For comparison purposes I pulled the bullets from several .223 factory rounds, dumped the powder charge and checked case capacity. The cases held from 28.7 to 29 grains of water.

Cartridges from the same box of ammunition were then fired in the ISSI chamber, resized, and their capacity measured. These held 32.5 to 32.7 grains of water, indicating a case capacity increase of 12 to 13 percent. The next step was to go through my current reloading manuals and check load recommendations for the parent .223 Rem. cartridge.

For each powder/bullet combination, I averaged the starting load from the different manuals. Since I knew case capacity of the Improved cases had increased by 12 to 13 percent, I felt it was safe to increase the starting load by 10 percent.

From this starting point it was simply a matter of increasing powder charges in .5-grain increments while watching for pressure signs. I consider a chronograph an essential tool for load development.

Experimental Loading Tip

Each powder increment should produce a velocity change that is roughly linear, and any change in that progression is a sign it's time to back off.

For example, let's say adding .5-grain of powder increases velocity 55 fps over the starting load. Another .5-grain addition shows a 62 fps gain, the next .5-grain addition a 52 fps increase.

Then, we add an additional one-half grain powder and gain only 20 fps (or conversely, jump up 100 fps). Any significant change such as this, or in extreme spread or standard deviation, should be considered a warning sign.

Test Components

Both Lee Mosher and I found powders recommended for the parent .223 Rem. case, particularly those on the medium/slow end of the range, produced excellent results in the .223 AI. These included Hodgdon BL-C2, W-W 748, Alliant's Reloder 12, and IMR-4064. Faster powders such as IMR-4198 and Reloder 7 gave good accuracy, but didn't achieve quite as high velocities at safe pressures.

Hodgdon H-335 seemed to work particularly well with the unit I had, with low extreme spreads and standard deviations and excellent accuracy. Mosher advised his personal favorites were two Accurate powders, AA-2460 and AA-2520.

Test bullets included the 40- and 50-grain Hornady V-Max, 50- and 55-grain Nosier Ballistic Tip, 52-grain Speer JHP, and Sierra 50-grain BlitzKing. Different powders, bullets, and individual strings of fire gave velocities in the following ranges: 55-grain bullets: 2,500 to 3,600 fps; 50-grain bullets: 3,650 to 3,750 fps and 40-grain bullets: 3,900 to 4,000 fps. These are about 250- to 300-fps faster than the same bullet weights in most factory .223 Rem. loads.

We used 26-inch barrels, while factory velocities are taken in 24-inch barrels, which likely accounts for about 70 to 100 fps velocity gain. Both Mosher and I are satisfied that these loads are safe in our individual rifles with the components and loading equipment we use.

And He's Not Satisfied Yet

With the prototype unit I was using, five-shot groups consistently averaged a bit better than 3/4 inch at 100 yards. Mosher got roughly the same accuracy with his unit. These, remember, were the first two he built. Although this is very good accuracy, it isn't as good as my older .223 Rem. ISSI unit. Based on experience with the two prototypes, Mosher had JGS make him a new reamer to his specifications.

The prototypes have a throat diameter of .254 inch. The new reamer cuts the barrel throat to a tighter .250 inch. The new reamer also cuts a slightly shorter throat than the original. With the shorter throat, bullets can be seated deep enough to fit and feed from the magazine and still have a short jump to reach the barrel lands. Another change was to go to a 1:14-inch twist, which Mosher felt was better suited to the lighter 40 and 50 grain bullets.

He has tried barrels from Lawrence Rifle Barrels and found they were equally as accurate as the fine Hart match barrels. He reports both makes of barrels cut with his new reamer have been producing superb accuracy, with many groups in the 1/4-inch range.

Other Details

In the course of firing some 200 rounds of standard 223 Rem. and 300 .223 AI cartridges the ISSI unit functioned perfectly.

"The AR-15 is almost perfectly suited to feeding the 40-degree case," Mosher commented, "better than most bolt guns."

Something I like to see with any semi-auto, rifle or pistol, is a consistent ejection pattern. Wanting to recover the cases while shooting the .223 AI unit from the bench, I noted where the first case lancteci, then set a range bag on the spot. From then on, just about every case ejected from the ISSI unit went spinning neatly into the bag.

Mosher does a lot of tuning and fitting to ensure smooth functioning. He found that the bolt locking lugs at the 1:30 and 3:00 positions tended to scratch cases. Relieving the edges of the lugs not only stopped the case scratching but led to a more consistent ejection pattern.

Latest Developments

Although both prototypes functioned reliably, Mosher felt the feed/ejection cycle could be smoother. On current models he slightly reduces the gas port diameter, and he now uses a Les Baer bolt and bolt carrier (1/4 ounce heavier than standard), and a chrome silicon recoil spring buffer from David Tubb. The result, he says, is superbly smooth operation.

Are improved cartridges worth the trouble? In his later years, P.O. Ackley himself seemed to doubt it. At the age of 63, he wrote:

"You cannot change the shoulder angle a few degrees and blow out the case a few thousandths and revolutionize the industry"

Guns & Ammo, March, 1970

The .223 AI may not be revolutionary, but it's an absolute charmer nonetheless. It is amazingly efficient in terms of velocity produced per grain of powder. Cases expand so little they scarcely seem to need trimming, and resizing is virtually effortless. With the .223 AI, performance nearly equals that of the .22-250 Rem., and the same rifle can still shoot economical .223 Rem. ammunition. That's an impressive combination.

 Factory rating from Les Baer
Load 24-inch barrel 20-inch barrel

Black Hills 50 gr. V-Max 3,300 3,251
Black Hills 52 gr. Match 3,300 3,253

Load 26-inch barrel

Black Hills 50 gr. V-Max 3,394
Black Hills 52 gr. Match 3,387


Insight Shooting Systems, Inc.,

P.O. Box 3525, Pueblo, Colo., 81005

[719] 564-8411

Redding Reloading Equipment

[605] 348-5150
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No portion of this article can be reproduced without the express written permission from the copyright holder.
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Article Details
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Author:Anderson, David Poole
Publication:Guns Magazine
Geographic Code:1USA
Date:Apr 1, 2003
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