Ackley Improved .....

**Andrew Leigh** · 23-12-2016, 10:49

Hi,

I have long mused over this subject, many of the lads over at Jaracal are firm believers in this "improvement" so I wanted to find out if there is any empirical data to back this up, after all it is an improvement. I also note that many AI improved calibres were "improved" after the passing of said Mr Ackley so I am left to assume at AI now refers to any change in the shoulder to increase the case volume.

So if the given calibre, which features the Ackley change in neck shape, there is an improvement then what is the improvement. If the improvement is simply to increase the cartridge volume then yes there is an improvement. If this allows for increased speed, well yes this may be seen as an improvement for some.

So then what exactly is the allure of an AI chambering, simply to have a hotter cartridge? If you want more clout why not by the appropriate standard calibre. I also understand that we have a need for development so I am not against changes in technology.

The real question is, "does the improvement materially affect the accuracy".

Three legs you must have been around the block a couple of times with this one, care to chime in?

Cheers

**Boomstomp** · 23-12-2016, 11:00

Ackley Improved does not only refer to the shoulder angle, he also used to take most if not all of the taper of the case away. Hence when calling something an AI everybody knows it means no taper and 40% shoulder.

One popular AI is the .243 AI. This is sometimes done for speed, but mostly it increases case life, takes away the donut-problem, and enables you to reach a given speed at less pressure.
There are some who state that the sharper shoulder angle moves the burning focus point into the neck of the cartridges, and out of the throat of the barrel... don't know how true that is.

AI does tend to work better with some calibers.

**WaldoH** · 23-12-2016, 11:16

I have been toying with the idea on my 30-06 as it has a minor head-space issue that I was hoping to address by converting to AI but I am not 100% certain if this can be done on my exiting barrel and the re-licensing debacle is a bit off putting. For this reason I have held off converting the gun to an IA model and have stuck with reloading my own ammo from once fired brass. I will be following this thread with interest.

**driepootx** · 23-12-2016, 11:34

Boomstomp quote

"One popular AI is the .243 AI. This is sometimes done for speed, but mostly it increases case life, takes away the donut-problem, and enables you to reach a given speed at less pressure."

This is exactly why I had my 243 done. The donuts and difficuty in chambering rounds are gone. I fired many of my old reloaded 243 rounds and got very good accuracy with them. The fact that you can shoot the original caliber's cartridges in the converted chamber is also a bonus and I did not do any relicensing. I can still buy and use a 243 cartridge and that is true for all AI conversions. The gunsmith must just ensure a tight headspace so that the case is not pushed away by the firing pin and poor ignition results.

Speed was not my main aim. I have shot 90gr Speer bullets in this rifle at 2950fps and they did very well on the shooting range. I try and keep to a pressure of 50-55K psi which gives good gas seal and accuracy. For my hunting loads with 80gr monos I do push up the speed to 3150fps.

**urabus** · 23-12-2016, 11:37

Originally Posted by driepootx

Boomstomp quote

"One popular AI is the .243 AI. This is sometimes done for speed, but mostly it increases case life, takes away the donut-problem, and enables you to reach a given speed at less pressure."

This is exactly why I had my 243 done. The donuts and difficuty in chambering rounds are gone. I fired many of my old reloaded 243 rounds and got very good accuracy with them. The fact that you can shoot the original caliber's cartridges in the converted chamber is also a bonus and I did not do any relicensing. I can still buy and use a 243 cartridge and that is true for all AI conversions. The gunsmith must just ensure a tight headspace so that the case is not pushed away by the firing pin and poor ignition results.

Speed was not my main aim. I have shot 90gr Speer bullets in this rifle at 2950fps and they did very well on the shooting range. I try and keep to a pressure of 50-55K psi which gives good gas seal and accuracy. For my hunting loads with 80gr monos I do push up the speed to 3150fps.

im now convinced to get my .243 & .260 AI'ed

**treeman** · 23-12-2016, 15:13

There is also the AI calibers thats seemed to offer almost no gain, if I recall the .270 and 223 were among these - I think it was the 270 that Ackley him self stated as about pointless.
I seem to remember the 308 was never AI,ed in his life time - only by others later on.

**Andrew Leigh** · 23-12-2016, 16:08

So Marius you do not regret your decision at all?

Did your .243 retain its original accuracy?

**Bonedoc** · 23-12-2016, 16:12

Originally Posted by treeman

There is also the AI calibers thats seemed to offer almost no gain, if I recall the .270 and 223 were among these - I think it was the 270 that Ackley him self stated as about pointless.
I seem to remember the 308 was never AI,ed in his life time - only by others later on.

No advantage ito velocity gained, but you will still have less brass flow and doughnuts with the 30 degree shoulder.

**driepootx** · 23-12-2016, 16:45

Originally Posted by Andrew Leigh

So Marius you do not regret your decision at all?

Did your .243 retain its original accuracy?

Do not regret it at all. Very sexy looking cases and if anything the the accuracy is more consistent with less flyers.

**WaldoH** · 23-12-2016, 22:16

My appologies for my ignorance but please elaborate on the licencing of an AI conversion. If I dont need to relicence my gun I would really consider this as altrernative to having the barrel rechambered / reamed / replaced to correct the headspace issue on my gun. Please also share any info on your experiece with 3006 AI. To my understanding with overseas powders the speeds could approach 300wm territory?