The real advantage of an Ackley

postoak

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The .280 AI is now a factory found, though, right?
 

Mekaniks

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Von Gruff

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It has been shown that with a 10% case capacity increase and at the same pressure there is only a 4% velocity increase.
I increased the capacity of the 6.5 Grendel case by moving the shoulder forward to make the Grendel-Max, but at the same time I loaded long (at 2.405 compared to 2.226 for the standard Grendel) for a much improved increase in the available case capacity than simply shifting the shoulder would have done, so gained quite a respectable velocity increase over the standard case. The standard Grendel is generally rated at about 2450fpr for the 123gn bullet from a 21-22 in barrel and I comfortably get 2700fps and superb accuracy from that barrel length.
 
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Let me begin by saying that I love the 6.5 x 55 Swedish Mauser (the original 1896 version.) Including the Swedes I have given to my grandchildren or plan to give them, there are just over a dozen of them in my safes. In order to reply to this question I went online to find out what the Ackley version of this fine old cartridge would do. In short 2900 fps with a 140 gr. bullet. My current load of 46.5 gr. of 4350 and a 140 gr. bullet is 2775 fps. To me the 4.5% increase in velocity isn't worth the trouble. If for some reason you really wanted to stick to the 6.5 caliber there are a number of options that would yield a greater boost in velocity like the 6.5 Creedmoor or the 6.5 x 284.
Shootist43
The way to work out the increase for the improved case is 4:1 rule.
For every 4% increase in capacity you get a 1% increase in velocity at the same pressure as the parent cartridge. Most gain comes from increased pressure in the improved case.
Cheers mate Bob
 

rookhawk

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Looking through my older notes, the 6.5x55 likes to be shot with compressed loads and about a 2750-2775fps for optimal accuracy.

The 6.5x284 was most accurate with less than compressed loads.

The net-net is if loading for optimal accuracy, the speed difference between the Swede and the 6.5x284/creedmore ends up being pretty negligible.

Of course, if 2950fps is the goal with the time-proven 140gr bullet, going to a copper bullet of the same volume (120-125gr copper) is going to get you into that super fast arena with a Swede anyway.

There is very little a Swede cannot do with “rounding error” advantages going to the aforementioned cartridges 100+ years newer.
 

fourfive8

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I am unsure about any great ballistic advantage to the Ackley cartridges. However, I am quite sure that some of them provide for more positive and consistent headspacing in some rounds. Plus, for marketing purposes, I guess adding the "Ackley Improved" suffix accounts for something.

I would not trust any of the Ackley published loads, even though ballistically they always look impressive. He did not use pressure equipment during his load development- he used the "something just short of action failure" method. :)
 

rookhawk

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I am unsure about any great ballistic advantage to the Ackley cartridges. However, I am quite sure that some of them provide for more positive and consistent headspacing in some rounds. Plus, for marketing purposes, I guess adding the "Ackley Improved" suffix accounts for something.

I would not trust any of the Ackley published loads, even though ballistically they always look impressive. He did not use pressure equipment during his load development- he used the "something just short of action failure" method. :)

Indeed, the ballistics of most Ackley's are just not worth the trouble. Ackley was a researcher and an experimenter. He made dozens of Ackleys and most of them were negligible improvements which is to be expected when you experiment. Others adhered to so many good principles that they inspired non-wildcat cartridges.

Of all that remain, there are about 4-5 AIs that are "worth the trouble", the most famous is probably the 280AI. Unfortunately, that is the most infuriating one because Nosler made 280AI a non-wildcat, SAAMI cartridge BUT DECIDED TO ALTER THE DIMENSIONS OF THE CARTRIDGE so you can't use factory 280ai ammo in a pre-SAAMI 280AI gun! Outrageous.

The other commonly found AI that is a gem is the 257 Roberts AI. However, the 257 Roberts AI has been surpassed by so many other .25s since then such as the 257 weatherby and the 25-06 that it doesn't seem to make sense. Add to that, for sturdy actions the modern 257 roberts +P ammo narrows the gap there quite a bit.

So would I ever own an AI? Only if in one of the calibers where 'it made a difference' and then only if it was in an American-Made mid-century best rifle as it was initially made. (e.g. Hoffman, Sedgley, Niedner, Griffin & Howe, etc.) That is only because I like fine American guns, not because I'm looking for trouble by trying to actively buy a wildcat gun.
 

bruce moulds

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22/250/250 savage will give a gain, as will 257 Roberts/7x57, and 6.5 swede, as the original cases are so tapered.
ackleying the 308 family is virtually a waste of time due to min body taper.
the 30/06 case in more like the 308 family.
375 h&h will give a gain, but do you need it in that situation?
as bob says, ackley data needs to be treated with respect for the reasons he said, but also because some powders have changed burning rate since then.
I thought I would like a 280 ackley, but have come to the conclusion I will stick to the std 280, as I have custom dies for my chamber and life is good.
bruce.
bruce.
 

bruce moulds

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here is another thought.
at one time the 25/06 ackley could easily equal the 257 weatherby in safe max velocities.
souds wrong, but true.
it is because the norma brass used then was too soft to retain primer pocket integrity compared to win or rem 30/06 brass.
the 25/06 ackley could simply be loaded to higher pressure, and in the real world could equal the 257 wby.
this had the added advantage of being able to own a 25 cal rifle with those ballistics that was affordable, and ammunition likewise.
one thing ackley improving does is reduce case length growth, which minimizes case stretching, and hence case head separations if the sizing die is correctly adjusted.
an example of a modern factory improved case is the 284 win.
problem with it is that it has a shorter neck than its ballistic twin the 280 rem, and hence shorter barrel life.
also to get the same performance as the 280 with heavy bullets, you need to use a 30/06 length action ant throat the chamber to suit.
bruce.
 
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22/250/250 savage will give a gain, as will 257 Roberts/7x57, and 6.5 swede, as the original cases are so tapered.
ackleying the 308 family is virtually a waste of time due to min body taper.
the 30/06 case in more like the 308 family.
375 h&h will give a gain, but do you need it in that situation?
as bob says, ackley data needs to be treated with respect for the reasons he said, but also because some powders have changed burning rate since then.
I thought I would like a 280 ackley, but have come to the conclusion I will stick to the std 280, as I have custom dies for my chamber and life is good.
bruce.
bruce.
Bruce
The old 303 or any of the 303 Wildcats really benefit as well from either the Epps or Ackley mods.
In a strong action like the P14 or Ruger No1 the 303 Epps will give the old 06 a good run for its money.
Bob
 
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bob, we tend to think in terms of case capacity, but brass strength and temper also have a lot to do with acceptable pressures.
bruce.
I couldn't agree more Bruce but with modern new brass all cases should have the same strength and temper.
I definitely wouldn't use old brass in my 25 or Whelen.
I want brass of good quality and mainly use Remington brass. Give long life. I'm in the process of trying Bertram brass in my 25. It looks good and you can still see the annealing Mark..
Cheers mate Bob
 

bruce moulds

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bob
in the black powder world, Bertram does not have a good name, for consistency or reliability.
do not go by an annealing mark.
it gives no guide to temp or time.
people started looking at that when lapua brass presented with annealing marks.
win, rem etc brass without the mark has also been annealed, but has the added process of a final polishing to remove the mark.
in actual fact the term annealing is a false one when applied to cartridge cases.
true annealing makes brass as soft as plasticine, so we partially anneal cases, more at the neck than the base.
norma brass used to be softer in the base than rem or win, and hence primer pockets opened up at less pressure.
you really need to partially anneal necks each shot or two to maintain consistent neck tension and maximize case life.
some of the most consistent and best brass I ever had was lake city match 30/06 brass.
I used it for 25/06, 6.5/06, 270, 30/06, and 35 whelen.
bruce.
 
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CBH Australia

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@Shootist43, I think you make a good point. In that case, it's not a worthwhile investment. Thank you very much, I'd say that itch has been satisfied, for now :p

As was said above, thanks to all who took the time to reply. Your comments are really appreciated and more helpful than you could imagine.

Again, thank you!
Thank you for posting there are some interesting and valid comments.
I might considering the .280ai, I note Bruce Moulds comments but as he says he already has the gear so there is no need to change I would be starting from scratch so if there is a gain to be had the time to do it is on the first build
 

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.280 AI has become my favorite medium game cartridge.
Can you tell us more about it, what are you hunting, the rifle setup,

Best bullet choice,
Is a 22” barrel enough ????
 
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Thank you for posting there are some interesting and valid comments.
I might considering the .280ai, I note Bruce Moulds comments but as he says he already has the gear so there is no need to change I would be starting from scratch so if there is a gain to be had the time to do it is on the first build
@CBH
Chris if your 7/08 is in a Tikka why not modify bolt stop change mag and jest get it rechambered to 280AI
Bob
 

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20” barrel
 
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bob
in the black powder world, Bertram does not have a good name, for consistency or reliability.
do not go by an annealing mark.
it gives no guide to temp or time.
people started looking at that when lapua brass presented with annealing marks.
win, rem etc brass without the mark has also been annealed, but has the added process of a final polishing to remove the mark.
in actual fact the term annealing is a false one when applied to cartridge cases.
true annealing makes brass as soft as plasticine, so we partially anneal cases, more at the neck than the base.
norma brass used to be softer in the base than rem or win, and hence primer pockets opened up at less pressure.
you really need to partially anneal necks each shot or two to maintain consistent neck tension and maximize case life.
some of the most consistent and best brass I ever had was lake city match 30/06 brass.
I used it for 25/06, 6.5/06, 270, 30/06, and 35 whelen.
bruce.
@bruce moulds
The Bertram 303 brass wouldn't even fit my chamber.
Rang him, his brass is in spec .457 to .480 where as everyone else makes it at .451. Fine for sloppy military chambers but not others.
Bob
 
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bob, we tend to think in terms of case capacity, but brass strength and temper also have a lot to do with acceptable pressures.
bruce.
@ Bruce moulds
The new brass is far superior to the old stuff. Never had a problem loading RP, Winchester, PPU, Hornaday or federal brass in my hot 25/303.
Bob.
 

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