280 AI alert

[J E Custom]

I am in the process of building two matching 280 AIs and after reading everything that
I could find I though I knew the way I wanted to go.

The desire was to simply place a 280 Rem in the 280 AI Chamber and fire form it.

And with all the rhetoric about Nosler changing the SAAMI dimensions I decided to
go with caution and use both head space gauges because I kept coming up with a
difference in the two as far as head space.

Wanting the fireforming process to also be accurate with the 280 Rem for hunting, I checked
head space often while chambering with both the 280 and the 280 AI go gauges and kept
coming up with the same difference.

Once the head space reached .000 with the AI gauge I checked it with the 280 Rem gauge
and had .0065 + , then I tried a loaded round and it was .006.(The bolt would not close on
the 280 Rem gauge).

So I chambered .006 deeper to allow the 280 Rem to head space, then I rechecked the
head space with the 280 AI gauge and had .006 thousandths(Two much).

This means that it would be possible to fire Nosler 280 AI in it but not advisable because
of the near Maximum head space.

All of the other AIs work great and are very accurate while fire forming, And why(I think I
know) they would make it this way Instead of just loading ammo with the AI head stamp
is beyond me. There is only one choice of ammo if you want the AI on the case head, but
there are dozens of choices for the 280 Rem.

My point of this post is to warn people about firing Nosler 280 AI in there 280 Ackley or
trying to get 280 Rem in one of the "New" AI chambers. (The only way you can find out
what you have is to have two head space gauges).

I buy lots of Nosler products but this will not be one of them.

Just my 2 cents.

J E CUSTOM

 

[shortgrass]

I don't know how Hornaday might change head space dimentions. When chambering an Ackley the "go" gage for the parent cartridge, in this case the .280 Remington, becomes the "no-go" for the Ackley chamber. Ackley chambers are shorter than their 'parent' cartridges. That way the case, when fire forming your .280 Rem. brass to .280 AI, is fully suported. Did I misunderstand your post? The bolt should close 'snuggly' on a .280 Rem. round when placed into a .280AI chamber.

 

[J E Custom]

I don't know how Hornaday might change head space dimentions. When chambering an Ackley the "go" gage for the parent cartridge, in this case the .280 Remington, becomes the "no-go" for the Ackley chamber. Ackley chambers are shorter than their 'parent' cartridges. That way the case, when fire forming your .280 Rem. brass to .280 AI, is fully suported. Did I misunderstand your post? The bolt should close 'snuggly' on a .280 Rem. round when placed into a .280AI chamber.

That is correct, and that is the way I chambered it but if I had used the new 280 AI head space
go gauge the 280 Rem would not chamber.

I talked to several reamer makers and they said that they have to cut there reamers to the "NEW"
dimension because it is the SAMMI spec now that Nosler has submitted it as the standard and
SAMMI has adopted it as submitted. You can still have a wildcat reamer cut but it will not be the
standard any more.(The old 280 AI reamers were cut like all the rest to use the parent case
head space gauge).

When I head spaced with the 280 AI go gauge the 260 Rem head space go gauge was .0065 to long
and the bolt would not close on the gauge, and on a factory round head space was .006 and still
would not close even with lots of pressure.

All of the other AIs use the neck to shoulder junction to head space the standard round and shoot
extremely good while fire forming.

I hear what you are saying about the go no go gauges but I can't make myself cut a chamber with
.006 Thousandths head space. originally I had thought about splitting the difference but decided
not to take a chance on the accuracy of the rifle and go with .0005 head space using the 280 Rem
head space gauge so there would be a little compression of the case on the bolt when closing.

So this way the chamber will be .006 longer than the NEW SAMMI 280 AI CHAMBER in order to
use the 280 Rem ammo.

I hope this explains the problem better.

Again maybe I'm to fussy about head space.

J E CUSTOM

 

[KRP]

I thought it was Nosler that did this? They are the only ones I know that make factory 280AI ammo/brass.

 

[FEENIX]

I thought it was Nosler that did this? They are the only ones I know that make factory 280AI ammo/brass.

Ditto!

 

[J E Custom]

I thought it was Nosler that did this? They are the only ones I know that make factory 280AI ammo/brass.

Sorry !!!!!
I did it again.Thanks for catching it.

It was Nosler.

J E CUSTOM

 

[Pdvdh]

I revive a 10-year old Thread. Because as recently as yesterday, the decade long debate and disagreement as to whether there is a difference in headspace between PO Ackley's traditional 280 AI, and Nosler's SAAMI adopted "280 Ackley Improved" cartridge continued, in a separate Thread on the Forum.

The answer is: The traditional 280 AI chamber headspace is 0.0142" longer (deeper) than Nosler's SAAMI "280 Ackley Improved". Below is the indisputable mathematical solution, and proof. The only level of math required is subtraction.

Below is the SAAMI "280 Remington (7mm Express Remington)" chamber drawing. Look at the drawing and find the Breech Bolt Face to neck/shoulder junction distance of 2.1924". This is the parent cartridge of PO Ackley'straditional 280 AI.

Here's the Nosler version, the SAAMI "280 Ackley Improved" chamber drawing. Look at the drawing and find the Breech Face to neck/shoulder junction distance of 2.1742".

P.O. Ackley's standard practice when improving a parent cartridge was to set the chamber neck/shoulder junction back 0.004" shorter than that of the parent cartridge. This ensured the bolt would close on the parent cartridge case with a 0.004" crush fit. This crush fit holds the parent cartridge case head in firm contact with the bolt face, so the case web doesn't stretch during the initial fire forming of the parent cartridge in the 'Ackley improved' chamber. This technique forces the parent case to instead, stretch in the shoulder area to fill the larger 'improved' chamber ID.

Let's begin the math - simple subtraction:
"280 Remington" breech bolt face to neck/shoulder junction distance from SAAMI = 2.1924". Reduce this distance by 0.004" in conformance with PO Ackley's standard practice, for Ackley improving the 280 Remington.
2.1924" - 0.004" = 2.1884" This is the breech bolt face distance to case neck/shoulder junction for Ackley's traditional 280 AI.

"280 Ackley Improved" breech face to neck/shoulder junction distance from SAAMI = 2.1742".

Subtract the smaller/shorter "280 Ackley Improved" 2.1742" distance from the from the larger/longer 2.1884" for the traditional 280 AI.

2.1884" minus 2.1742" equals... 0.0142"

Since both cartridges share the same 40-degree shoulder angle, the 0.0142" difference is maintained at any common datum point along their shoulders.

It should come as no surprise that J E Custom had it nailed down correctly from the very get-go.

 

[bowhand]

I revive a 10-year old Thread. Because as recently as yesterday, the decade long debate and disagreement as to whether there is a difference in headspace between PO Ackley's traditional 280 AI, and Nosler's SAAMI adopted "280 Ackley Improved" cartridge continued, in a separate Thread on the Forum.

The answer is: The traditional 280 AI chamber headspace is 0.0142" longer (deeper) than Nosler's SAAMI "280 Ackley Improved". Below is the indisputable mathematical solution, and proof. The only level of math required is subtraction.

Below is the SAAMI "280 Remington (7mm Express Remington)" chamber drawing. Look at the drawing and find the Breech Bolt Face to neck/shoulder junction distance of 2.1924". This is the parent cartridge of PO Ackley'straditional 280 AI.

View attachment 247736

Here's the Nosler version, the SAAMI "280 Ackley Improved" chamber drawing. Look at the drawing and find the Breech Face to neck/shoulder junction distance of 2.1742".

View attachment 247740

P.O. Ackley's standard practice when improving a parent cartridge was to set the chamber neck/shoulder junction back 0.004" shorter than that of the parent cartridge. This ensured the bolt would close on the parent cartridge case with a 0.004" crush fit. This crush fit holds the parent cartridge case head in firm contact with the bolt face, so the case web doesn't stretch during the initial fire forming of the parent cartridge in the 'Ackley improved' chamber. This technique forces the parent case to instead, stretch in the shoulder area to fill the larger 'improved' chamber ID.

Let's begin the math - simple subtraction:
"280 Remington" breech bolt face to neck/shoulder junction distance from SAAMI = 2.1924". Reduce this distance by 0.004" in conformance with PO Ackley's standard practice, for Ackley improving the 280 Remington.
2.1924" - 0.004" = 2.1884" This is the breech bolt face distance to case neck/shoulder junction for the Ackley's traditional 280 AI.

"280 Ackley Improved" breech face to neck/shoulder junction distance from SAAMI = 2.1742".

Subtract the smaller/shorter "280 Ackley Improved" 2.1742" distance from the from the larger/longer 2.1884" for the traditional 280 AI.

2.1884" minus 2.1742" equals... 0.0142"

Since both cartridges share the same 40-degree shoulder angle, the 0.0142" difference is maintained at any common datum point along their shoulders.

It should come as no surprise that J E Custom had it nailed down correctly from the very get-go.

Being someone who has dreamed of owning a 280 Ackley for as long as I can remember, this is all very discouraging news! Another issue I see in addition to headspace is the head diameter of the 280 Ackley(s). Why in the world would the head diameter be smaller than the 30/06? The chambersmith at LRI pointed out that I can't safely have a 7mm-08 rechambered to 280 Ackley because the head dia of the reamer is too small to clean up the 7mm-08 chamber. The 280 Rem is not an option either because that reamer won't clean up the shoulder of the 7mm-08.

 

[FEENIX]

@J E Custom, RIP Brother. Thanks for sharing your knowledge and real-world experiences. You are always willing and able to lend a helping had.

You will be sorely missed by many of us.

V/R
Ed

 

[Pdvdh]

Being someone who has dreamed of owning a 280 Ackley for as long as I can remember, this is all very discouraging news! Another issue I see in addition to headspace is the head diameter of the 280 Ackley(s). Why in the world would the head diameter be smaller than the 30/06? The chambersmith at LRI pointed out that I can't safely have a 7mm-08 rechambered to 280 Ackley because the head dia of the reamer is too small to clean up the 7mm-08 chamber. The 280 Rem is not an option either because that reamer won't clean up the shoulder of the 7mm-08.

I didn't think, or know, there was any substantial difference in the breech face SAAMI chamber diameters of the 7mm-08, 280 Rem, 280 Ackley Imp, 308 Win, or 30-06 Springfield.

So out of curiousity, I researched SAAMI chamber specs for the breech face diameters all of these SAAMI adopted cartridges. There are some slight differences. Only LRI could decide if the differences preclude their ability to agree to your request for such a re-chambering.

Diameters at Breech Face. . . . Diameters 0.200" forward of Breech Face
7mm-08_ _ _ _ _ 0.4738". . . . . . 0.4714"
280 Rem_ _ _ _ _ 0.4747" . . . . . 0.4714"
280 Ack Imp _ _ 0.4727" . . . . . 0.4710"
308 Win _ _ _ _ _0.4738" . . . . . 0.4714"
30-06 Sprng _ _ 0.4740" . . . . . 0.4708"

I couldn't see any issue rechambering to the traditional 280 AI. Because the parent case, the 280 Rem diameters are the same at the 0.200" datum, and 0.0009" larger in diameter than the 7mm-08 at the breech face. But you would then have to fire form 280 Rem casings to 280 AI, rather than using the pre-formed 280 Ackley Improved casings available for Nosler's SAAMI version.

Evidently, Nosler also messed with the breech face diameter when pursuing SAAMI adoption of their "280 Ackley Improved". It's actually only 0.002" smaller in diameter at the breech face than the 280 Rem & traditional 280 AI.

 

[antelopedundee]

I am in the process of building two matching 280 AIs and after reading everything that
I could find I though I knew the way I wanted to go.

The desire was to simply place a 280 Rem in the 280 AI Chamber and fire form it.

And with all the rhetoric about Nosler changing the SAAMI dimensions I decided to
go with caution and use both head space gauges because I kept coming up with a
difference in the two as far as head space.

Wanting the fireforming process to also be accurate with the 280 Rem for hunting, I checked
head space often while chambering with both the 280 and the 280 AI go gauges and kept
coming up with the same difference.

Once the head space reached .000 with the AI gauge I checked it with the 280 Rem gauge
and had .0065 + , then I tried a loaded round and it was .006.(The bolt would not close on
the 280 Rem gauge).

So I chambered .006 deeper to allow the 280 Rem to head space, then I rechecked the
head space with the 280 AI gauge and had .006 thousandths(Two much).

This means that it would be possible to fire Nosler 280 AI in it but not advisable because
of the near Maximum head space.

All of the other AIs work great and are very accurate while fire forming, And why(I think I
know) they would make it this way Instead of just loading ammo with the AI head stamp
is beyond me. There is only one choice of ammo if you want the AI on the case head, but
there are dozens of choices for the 280 Rem.

My point of this post is to warn people about firing Nosler 280 AI in there 280 Ackley or
trying to get 280 Rem in one of the "New" AI chambers. (The only way you can find out
what you have is to have two head space gauges).

I buy lots of Nosler products but this will not be one of them.

Just my 2 cents.

J E CUSTOM

FYI Peterson Cartridge offers .280 RemAI brass.

https://www.petersoncartridge.com/match-grade-brass/brass-rifle-casings/280-ackley-improved/

 

[sturner]

R I P JE

 

[WItoOR6637]

Wow there is a ton of info here. Sorry to hear JE passed.

 

[carlbobh]

I was fortunate to build a 280 AI with JE on a Remington Model 30 action .. labeled it as Rem 280 Imp 40 Deg, as was on the Manson Reamer. It's my go to for just about anything.