# To AI or not to AI



## Bo0YaA (Sep 29, 2008)

So I'm really digging the .260 and have even considered moving up to the 6.5x284. I was mentioning the idea to a friend of mine who suggested I just AI my .260. Now I have never owned any caliber in the AI configuration but it doesn't take long on the web to find that there most defiantly benefits to doing it. I guess my question is, are the benefits worth the $150.00 $200.00 it costs to have it reamed? It looks to me like with regards to the .260 its only adding about 150-200 FPS which is good but how about dealing with brass new dies and so on. 

SS I figure this question is right up your alley


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## Springville Shooter (Oct 15, 2010)

I'll start by saying that I LOVE my Ackley's! That being said, there are very few instances where AI cartridges don't duplicate other commercially available offerings. ie the 257AI duplicates the 25-06, the 280AI duplicates the 7mm Rem Mag etc. So, if it is solely performance that you seek, you might look into rechambering to another standard cartridge. I like the Ackley cartridges because they are a tribute to a great wildcatter in PO Ackley. They are also somewhat unique, offer great case life, and can mildly increase performance. If these things matter to you, then you will enjoy your Ackley's like I do. 

In your specific case, the 260 Ackley will not duplicate the performance of the 6.5-284. It will, however allow you to get a little more performance from your 260 while increasing case life during repeated firings. 

As far as the brass, I simply fire form mine during initial barrel break-in. After that, the Ackley brass will hardly stretch making case life very long. I average a trimming every 4-5 loadings with Ackley brass. You can leave the stuff in your will. The dies will cost you a bit more than standard depending on the caliber.

I have, or have had the following and can help with specific loads:

223AI
22-250AI
6mmAI
257AI
25-06AI
280AI
308AI
30-06AI
338-06AI

Yes, I have a sickness.------SS


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## DallanC (Jan 13, 2009)

What velocities are you getting out of that 22-250AI? That has me intrigued, definitely would improve brass life.

-DallanC


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## Springville Shooter (Oct 15, 2010)

My 22-250AI is a custom job with a 24" Shilen Barrel on a Howa action. My favorite load shoots 55 gr ballistic tips very accurately at 3850FPS. I traded the rifle to a buddy and he experimented with a few different loads before circling back to my load. If I build another 22-250AI, I would like to use a fast twist barrel and shoot 75-80 grain long range bullets. This would be a great rifle for shooting golf balls at 600 yards.
You are absolutely correct about case life increasing, especially with a tapered case like the 22-250.--------SS


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## longbow (Mar 31, 2009)

I love my AIs! You could rechamber cheaper than buying a new barrel. The real reason is I just love weird, different and odd calibers. I might be sick too.


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## Bo0YaA (Sep 29, 2008)

I realize I would not duplicate the performance of the 6.5x284 but from what I have read I could get within 150fps or so. I think the real appeal is in the brass, .243, 7mm-08 or even 308 brass are much cheaper and readily available for a good price and are easy to turn into a .260AI where as the 6.5x284 is a little harder to find and much more expensive. SS & Longbow, who do you have do your reaming if you don't mind me asking?


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## Frisco Pete (Sep 22, 2007)

The reality is that at accepted pressure levels - on a percentage basis you will can exactly gain 1/4 of the powder capacity increase as a velocity increase over the parent cartridge.
John Barsness' 1 to 4 improvement ratio rule applies here.

For an actual example of the 1/4 Rule given in Guns magazine in April 2009 by John Barsness who has done extensive research on the Improved subject: 
A 35 Whelen case held 63.1 grains of water with a 250-gr Hornady SP seated to the cannelure. A .35 Improved case held 67.2 grains, an increase of 6.5% in powder room. This sounds like a lot until we divide 6.5 percent by 4, and find the potential increase in muzzle velocity is 1.6% or about 40 extra fps of muzzle velocity given the parent pre-AI round of 2500 fps.
This is a far cry from 150-200 fps estimated by the late gun writer for his Whelen Improved.

However many loaders of AI cartridges often claim they reach those 150-200 fps speeds. If they actually do when chronographed, it is more due to the round being loaded to excessive pressure than any magic that a small 6-8% increase in powder capacity would give. John Barsness tested some of these properly fast 150-200 fps faster AI loads in an industry standard pressure test and found this was invariably the case. There was no magic in the case shape that allowed for such velocity gains with such a small increase in case size at standard pressures. Not having tested data allows the handloader to be free of those pesky limits set by reloading manuals. Of course you can just overload the standard cartridge and arrive at the same destination - minus 50 fps or so depending on the increase the AI would give in capacity.

Exceptions to this are sloping cases like the original H&H cases and rounds that are perennially under loaded by the factory like the .257 Roberts.

The .260 Rem with its more modern .308-based case and straighter shoulders will not likely see any improvement that exceeds the 1/4 rule unless you overload the powder charge due to a lack of pressure-tested loading data for the AI version. The 7mm STW was a lot hotter/faster as a wildcat until it became a factory round and was subjected to the same pressure testing as rounds like the 7mm Rem Mag.

One reason the AI shooters don't seem to notice the higher than accepted pressure is that the stable case design of the AI masks pressure signs very well. This is not all bad, as it is the reason for longer case life and less case stretch. However, loaded to acceptable pressures it is unlikely that the AI will gain you any more than 50 fps over existing handloads. The increase over factory ammo is likely more, but we all know that.

Cases will last longer. However one has to realize that for the cost of improving your rifle and buying dies you can buy another 350-400 factory .260 cases.

There is nothing wrong with AI-ing your rifle - but the benefits are very slim other than the great feeling you have by owning something unique and faster, and being able to tinker around with handloads more. And you would become a member of the very exclusive and posh AI Club. That is about as close to becoming a Sorcerer as you can do nowadays.


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## Springville Shooter (Oct 15, 2010)

Pete brings up some good points and I would add that even a 150-200 FPS gain doesn't really change the overall ability of the rifle. Bottom line is not to expect to kill bigger animals or to be able to shoot farther with an improved cartridge. Then again, the same can be said about the 308 vs the 30-06. I don't have a pressure guage and use a ballistic program to project pressures. Using projected velocities as a measure, I'm assuming the program is fairly accurate. Personally I am achieving the 150-200 FPS gains while staying within pressure specs. The biggest key for me is that I can achieve higher velocities accurately. My 25-06AI shoots 100 grain bullets at 3500 fps. You could approach 3400 by overloading a standard 25-06 but I bet you would be hard pressed to see the 1/3MOA accuracy that I get with the Ackley. You could, however, simply go to a 257 Weatherby and exceed the performance of the Ackley.

IF I am running over pressure, I am getting 8-10 firings on each case with no pressure signs, no stretching, no measurable head expansion, and no primer pocket expansion. Over the years I have lost more Ackley cartridges by dropping them on the ground than I ever have from case failures. Also, many of my rifles still shoot sub MOA with standard rounds. My 223 Ackly will shoot standard 223 loads into bughole sized groups. I often fireform cases while shooting prarie dogs.

Lastly, don't discount the benefits of case design. I think its more than coincidence that the most accurate/precision rounds in the world exhibit features such as little case taper and sharp shoulders. Some examples are the RUM, WSM, BR, PPC, XC, 284, Creedmore, and 47 based cartridges.

In a world where people experiment with brands of primers and ream case necks to increase performance and accuracy, the Ackley advantage starts to look pretty significant. -------SS


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## Loke (Sep 7, 2007)

The problem with over pressure loads is not whether or not your cases last for 3, 6. or 18 loadings. The biggest issue is one that most folks never consider. That would be the metal fatigue caused by repeatedly over stressing your rifles action. Your brass case may not show any signs of pressure until you are up in the 75-80,000 psi range. Meanwhile, your bolt lugs are over flexing and, just like a piece of wire that you break by bending over and over, developing cracks that could let go and send the rifles bolt into your face. It happened to a kid from my town that was a couple of years younger than me. He was using factory ammo at the time, but the gun had been used to "experiment" with some 7mm handloads. Just one reason I tend to shy away from used guns, especially when I know the people they come from.


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