What is Ackley improved

[pdugas]

Could someone please explain what A.I. means ?

Thank you in advance

 

[ShtrRdy]

basically it's a steeper shoulder angle with the thought of being able to hold more powder and getting more velocity.

Here's a link to some information and a picture of a .243 Win alongside a .243 AI
https://en.wikipedia.org/wiki/P.O._Ackley#Wildcats_and_Ackley_Improved_Cartridges

 

[pdugas]

Thank you for the reply

 

[lazylabs]

Buy his two book set, outdated but interesting reading.

 

[J E Custom]

Back when PO Ackley was at his best there were lots of standard cartridges with limited powder
selections. He did lots of testing to se if these cartridges could be improved by re shaping the case.

he tested many different shoulder angles and body tapers to see if the cartridge could be "IMPROVED" with the existing powders of the time.

He found that the 40o shoulder seemed to give the best results and less body taper Also, than
normally thought to be best.

These changes not only gave the case more powder capacity (Allowing a slower burning powder)
The changes gave the brass better life. (The case does not grow as much at firing that would require
trimming often) and causing case thinning.

It also allows a standard chamber to be cleaned/freshened up and standard ammo can still be fired in the AI chamber.

With the new powders, in most cases the AI version will out perform there big brother. (The 280 Rem, for example can out perform the 7 Rem Mag in most cases with less powder.

So the Ackley Improved designation means better performance and better brass life when loaded to SAMME pressures.

Hear are the SAMME chamber differences for the 280 for comparison.

http://www.saami.org/PubResources/CC_Drawings/Rifle/280 Remington - 7mm Express.pdf

http://www.saami.org/PubResources/CC_Drawings/Rifle/280 Ackley Improved.pdf

J E CUSTOM

 

[Mikecr]

Ackley provided a well thought out standard for cartridges.
There are many wildcats today that are similar in design, and successful.

 

[Bart B]

When comparing Ackley Improved cartridges to others, ensure each produces SAAMI spec or equal pressures in spec test barrels. Visible or measured primer and cases for differences are not precise enough for fair and realistic comparison. Nor are non-spec chamber, bore and groove diameters and lengths.

SAAMI specs for 140-gr. bullet in each with .2770" bore, .2837" groove, 24" barrel. and spec'd chambers:
280 AI, 65,000 psi, 3260 fps.
7 R.M., 61,000 psi, 3085 fps.

Wonder what the 7 Rem Mag would do with a 140 and 65,000 psi? 3261 fps?

 

[J E Custom]

When comparing Ackley Improved cartridges to others, ensure each produces SAAMI spec or equal pressures. Visible or measured primer and cases for differences are not precise enough for fair and realistic comparison.

+1
what he said.

Comparing cartridges should be at the same SAMME pressures to get fair comparisons (Apples to apples) also barrel lengths should be taken in to consideration.

J E CUSTOM

 

[FEENIX]

basically it's a steeper shoulder angle with the thought of being able to hold more powder and getting more velocity.

Here's a link to some information and a picture of a .243 Win alongside a .243 AI
https://en.wikipedia.org/wiki/P.O._Ackley#Wildcats_and_Ackley_Improved_Cartridges

An extract from the link provided above ...

NOTE: The term "Ackley Improved" has been applied by various gunsmiths conceptually to many cartridges not extant during P.O. Ackley's lifetime. By P.O. Ackley's definition of Improved, a firearm so chambered must be capable of shooting the factory original round, also such cartridge case either necked up or down to a different bullet size, without stretching the case. To accomplish this, the chamber for a rimless bottle necked "improved" cartridge must be somewhat shorter in the body than the original so that there is no headspace when the round is chambered.

My .270 AI ...

(.270 Win 150 NBT vs .270 AI 175 Matrix VLD)

 

[Trickymissfit]

Buy his two book set, outdated but interesting reading.

the only thing seriously dated in Ackley's books are his metallurgy.
gary

 

[Morrison]

In my efforts to find the perfect gun.... I have acquired 3 of the 280 AI built off of Mauser actions. My personal thoughts are that it is equal to the 7mm RM when using 140 grain bullets and is more efficient with the powder. When you move to heavier bullets it falls a bit short, about 100 fps using the 160 grain bullet. However, when compared to the 30-06 or the 270 it turns out to be superior to both. It has the flat trajectory of the 270 with far more available quality bullets and has the down range effectiveness of the 30-06.

I think it is proper to keep the point in time that Ackley was doing this development in mind. It was after the war and there was a lot of 30-06 brass available and limited powder options. The large selection of Magnums that we have today were not available.

BTW, this did finish in the top 3 calibers for my perfect gun. It will do anything that you ask of it, when you load it correctly.

 

[TOM H]

Nosler has loading data for SAAMI spec 280AI/26" barrel with their 140gr bullet and max velocity @ 3265fps. They also have data for 7mag/24" barrel with 140gr max @ 3340 fps.

Hodgdon also has SAAMI spec data for both including pressure.

John Barsness has written many articles on equal pressure for the Ackleys on 24 hr.

I shoot 27" barrel 280AI.

 

[LoneTraveler]

Mr. Parker O. Ackley was at the front of developing higher velocity. Without having to purchase another rifle in Magnum caliber. Just have your existing rifle re-chambered to his Improved Chamber. Hodgdon 4831 powder was in his inspiration to make improvements of standard cartridges with more capacity.
I have read a lot of articles by Mr. Parker O. Ackley on improving performance of standard cartridges to near Magnum with just enlarging case volume a bit and changing the shoulder on factory cartridges.

In the Era of 1945 to about 1965 was a great development time in Target and Hunting Rifles in the USA.

Parker O. Ackley Improved standard cartridges to near magnum performance.

Roy Weatherby developing his rounded radious shoulder cases and long throat chambering to get more velocity.

Winchester developed the 338 WM an 264 WM 300 WM in plan

Remington developed 7MM Rem. Mag.

Herters was using a double step shoulder on H & H Mag. cases in their quest for more velocity.

Norma developed the 300 NM and 358 NM mainly for USA sales.

And Hodgdon Powder Co. started supplying military surplus powder 4831 (Now becoming known as H4831) In the early time of its availability it was also know as 4350 DATA powder, Because IMR 4350 data could be safely used, Till 4831 data was developed and tested. Many standard cases you could not get enough powder in with even heavy bullets to reach the powders potential.
At .75 (Seventy Five Cents) pound in lots of 50 pounds of paper bags, plus freight it was cheap for developing and using this powder.

This era was the birth of many high velocity development in rifle cartridges. This brought a demand for better scopes to use these calibers to there capability.

Then all development seemed to stand still, Even with many new slower powders being developed until some one looked back in history. When someone seen a 404 Jeffery Case OH BOY. Then USA companies started the Ultra Mag and Short Mag rage of the last 20 years of so.

Just an old hunter and reloader going back down memory lane.

 

[Longtooth32]

An extract from the link provided above ...

My .270 AI ...

(.270 Win 150 NBT vs .270 AI 175 Matrix VLD)

Those look like a skinny 270 Wby ...very nice...

How much extra case capacity are you getting out of your 270AI?

Thanks...