280 Ackley Chamber

DirectDrive

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I know that this has been hashed and re-hashed.
I've searched everywhere and conversations seem to end in a giant axle-wrap.
Some say that you can fire a factory Nosler 280AI or Federal AI round in a SAAMI chamber.
Nosler has been quoted as saying not to fire Nosler ammo in the "old Ackley" chamber.
Maybe that's a CYA statement ?

Here's my dilemma :

1) I would like my rifle to be able to safely shoot Nosler and Federal ammo.
2) My smith only has the old Ackley reamer.
3) Can the old reamer be used for this ?
4) How much "jump" is max for the factory ammo ?

What if I used this information to set my throat ?
My mag box is 3.7" and I would like to shoot 168gr Bergers when I can find them.
 

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shortgrass

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Current Nosler and Federal .280AI is manufactured to SAAMI specs, so I'd head space the chamber to current SAAMI specs if that is what you want to shoot. The traditional .280AI reamer will work for this, just make sure the person doing the chambering uses head space gauges made to the current SAAMI specs. I have a .280AI that I built on a Rem 700 LA. I used the new, SAAMI spec reamer and gauges and set the head space at "GO" + .002". I have a bunch of Winchester head stamp .280 Remington brass, so I am fire forming that to my SAAMI chamber. The Win brass doesn't "crush" in the SAAMI chamber, so I am seating the bullet long, into the rifling, and that keeps the base of the cartridge against the bolt face. That is what you want, as it forces the case to stretch to the chamber at the shoulder instead of creating a bulge at the head. With all the variation in lengths of factory loaded ammo these days, I'd not count on being able to fire form factory in my AI chamber. Confused more, now?
 

Troutslayer2

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Current Nosler and Federal .280AI is manufactured to SAAMI specs, so I'd head space the chamber to current SAAMI specs if that is what you want to shoot. The traditional .280AI reamer will work for this, just make sure the person doing the chambering uses head space gauges made to the current SAAMI specs. I have a .280AI that I built on a Rem 700 LA. I used the new, SAAMI spec reamer and gauges and set the head space at "GO" + .002". I have a bunch of Winchester head stamp .280 Remington brass, so I am fire forming that to my SAAMI chamber. The Win brass doesn't "crush" in the SAAMI chamber, so I am seating the bullet long, into the rifling, and that keeps the base of the cartridge against the bolt face. That is what you want, as it forces the case to stretch to the chamber at the shoulder instead of creating a bulge at the head. With all the variation in lengths of factory loaded ammo these days, I'd not count on being able to fire form factory in my AI chamber. Confused more, now?
Man do I wish I knew this years ago. In my opinion having had both a traditional and SAMMI chambers the answer is NO, unless you do what shortgrass says and jam the bullets in the lands. If it were me I’d ask my smith to get the SAAMI reamer if I wanted to shoot the brass that is head stamped 280AI.
 

shortgrass

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To further add to the confusion; my rifle is head spaced using the new, SAAMI gauges ("GO" = .002"). Yet, the bolt will close on the "GO" .280 Remington gauge. P.O. Ackleys' method for his "Improved" says "the "GO" gauge for the 'parent' cartridge (the 'parent' cartridge being the .280 Remington) becomes the "NO-GO" for his improved (the bolt should not close on the .280 Rem. "go" gauge).....
 

DirectDrive

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To further add to the confusion; my rifle is head spaced using the new, SAAMI gauges ("GO" = .002"). Yet, the bolt will close on the "GO" .280 Remington gauge.
This doesn't add up for me.
I thought that one of the features of the Ackley system was to be able to fire-form parent cartridges in the Ackley chamber ?

Therefore, with the SAAMI chamber being LONGER than the Traditional Ackley, the .280 Rem GO gauge SHOULD let the bolt close when said gauge is in a SAAMI chamber.
SAAMI chamber = longer______.280 Rem gauge = shorter
P.O. Ackleys' method for his "Improved" says "the "GO" gauge for the 'parent' cartridge (the 'parent' cartridge being the .280 Remington) becomes the "NO-GO" for his improved (the bolt should not close on the .280 Rem. "go" gauge).....
This I can "get" because maybe Ackley wanted a little "crush" when the parent case was chambered to ensure safe headspace ?

So unless I get confused again, it appears that the smart money, when chambering a .280 Ackley in 2021, is to chamber SAAMI compliant and then throat for the bullet(s) that you want to use.
 
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shortgrass

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Every Ackley Improved chamber, that P.O. Ackley himself designed, is shorter in length/depth ( by .004-.006") than the parent cartridge. The parent case inserted into the Improved chamber is "trapped" between the bolt face and the neck/shoulder junction. This insures that when the cartridge is fired that it will stretch at the front shoulder to meet the chamber (fire form), and not at the rear where you need the the strength (thickness) of the brass case. I have chambered, in my shop, .220 Swift AI, .223 AI, .22/250AI, .243 AI, 6mm Rem AI,.257 Roberts AI, .260 Rem AI, .280 Rem AI, and .338/06AI. These are all done in the 'traditional' manner as prescribed by P.O. Ackley. Only the new SAAMI version of the .280 AI seems to give trouble to those who are new to the Ackley Improved cartridges. I have the newer SAAMI .280 AI reamer and head space gauges and give my client the choice when I get a chamber job for that one. On a 'hunting' rifle I generally chamber to the "GO" gauge + .002" deeper (hey, the idea of the Ackley Improved is to increase case capacity and 'improve' the shoulder for better combustion of the propellant, isn't it?). In this way the reloader has no trouble 'bumping' the shoulder back a bit with any production sizing die. Not everyone is willing or can afford to run out and order a custom sizing die if an 'off the shelf' RCBS or Redding isn't working for them. I will chamber to "GO" + .000" upon request. The .280 AI is the only improved that seems to give some people problems. There is a lot of disagreement among gunsmiths and gun writers about the .280AI verses the .280 traditional Ackley. I have been chambering since '92, and I have been machining since '74. All I can do is relay my personal experience with the .280 Improved cartridges. Both of my .280 AI reamers and gauge sets were made by Dave Mansons' shop.
 
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DirectDrive

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Every Ackley Improved chamber, that P.O. Ackley himself designed, is shorter in length/depth ( by .004-.006") than the parent cartridge. The parent case inserted into the Improved chamber is "trapped" between the bolt face and the neck/shoulder junction. This insures that when the cartridge is fired that it will stretch at the front shoulder to meet the chamber (fire form), and not at the rear where you need the the strength (thickness) of the brass case. I have chambered, in my shop, .220 Swift AI, .223 AI, .22/250AI, .243 AI, 6mm Rem AI,.257 Roberts AI, .260 Rem AI, .280 Rem AI, and .338/06AI. These are all done in the 'traditional' manner as prescribed by P.O. Ackley. Only the new SAAMI version of the .280 AI seems to give trouble to those who are new to the Ackley Improved cartridges. I have the newer SAAMI .280 AI reamer and head space gauges and give my client the choice when I get a chamber job for that one. On a 'hunting' rifle I generally chamber to the "GO" gauge + .002" deeper (hey, the idea of the Ackley Improved is to increase case capacity and 'improve' the shoulder for better combustion of the propellant, isn't it?). In this way the reloader has no trouble 'bumping' the shoulder back a bit with any production sizing die. Not everyone is willing or can afford to run out and order a custom sizing die if an 'off the shelf' RCBS or Redding isn't working for them. I will chamber to "GO" + .000" upon request. The .280 AI is the only improved that seems to give some people problems. There is a lot of disagreement among gunsmiths and gun writers about the .280AI verses the .280 traditional Ackley. I have been chambering since '92, and I have been machining since '74. All I can do is relay my personal experience with the .280 Improved cartridges. Both of my .280 AI reamers and gauge sets were made by Dave Mansons' shop.
That all makes perfect sense.
I think now that the SAAMI is on the table, one has to decide...
1) Do I want to fire-form my cases and go traditional Ackley ?
2) Do I want to use new, 280 Ackley brass/ammo and go SAAMI chamber ?

The confusion if any is...
Can I safely fire Nosler/Federal factory ammo in a traditional chamber ?
Some say no and some say yes.
When you look at the math, it says no, you shouldn't fire factory ammo in the traditional chamber.
 

phorwath

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That all makes perfect sense.
I think now that the SAAMI is on the table, one has to decide...
1) Do I want to fire-form my cases and go traditional Ackley ?
2) Do I want to use new, 280 Ackley brass/ammo and go SAAMI chamber ?

The confusion if any is...
Can I safely fire Nosler/Federal factory ammo in a traditional chamber ?
Some say no and some say yes.
When you look at the math, it says no, you shouldn't fire factory ammo in the traditional chamber.
The math and Redding do say no. I've done the math myself and it's 0.014" no-go difference in headspace between the two.
Decide which one you want and proceed. if you intend to use brass manufactured for the newer SAAMI 280 AI specs don't wanna fuss with fire-forming to the 0.014" longer headspaced traditional Ackley chamber, then better headspace your chamber to the SAAMI spec.

I got into a real shootout on the Shooters' Forum with some 'experts' that all proved to be less than expert. The entire Thread was eventually deleted after I embarrassed some of that Forum's longstanding 'experts' who claimed there was no difference in headspace dimension between the traditional 280 Ackely and the SAAMI 280 AI. Somehow those experts convinced themselves that Redding, who's been manufacturing reloading dies since Adam and Eve, was wrong about the 0.014" headspace difference. Been in business forever, and Redding continues to stand by their correct description of the 0.014" difference. It was all too funny when all was said and done.

shortgrass followed that now-deleted Thread. shortgrass has it 100% correct.
 

fraz01

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There is an article on the Gunsmith Talk web site posted July17, 2012. Article is 280 Ackley Improved Emperical Headspace Test. It is a good read that is well illustrated. Not trying to take your thread into the weeds here. A good gunsmith and correct reamer along with Go/No-Go gauges with proper spec's should produce a trouble free rifle.
 

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