280 Ackley Chamber

[DirectDrive]

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.

Maybe I did my math wrong, but I come up with the SAAMI chamber being the longer chamber of the two.
Longer by .013" (.0134) at the NS intersect.
And longer by .011" (.0111) at the start of the shoulder.

From the prints at 4D Reamer Rentals...

Traditional

SAAMI

 

[shortgrass]

A worthwhile read: "Handbook for Shooters and Reloaders", consists of 2 books written by P.O. Ackley. It doesn't address the new SAAMI spec .280AI, but it is "the" reference when it comes to all the other Ackley Improved cartridges. Here's another read; https://www.redding-reloading.com/tech-line-a-tips-faqs/133-280-changes I normally don't go to places like reamer rental companies when I need to compare prints. Those may be correct, but to be honest I didn't even look at 'um. I go to www.saami.org for industry standards. The 'traditional' .280 Ackley won't be listed there as it is a 'wildcat'. If I need a print of a 'wildcat' I go to JGS or Dave Manson. PTGs' customer service is so poor I'd trust nothing provided by them. With the current unavailability of all things related to reloading I would opt for the SAAMI unless you are willing to spend for a custom made die set. By the way, there is no 'factory' .280 Remington on the shelf, either,,, to fire form in a 'traditional' chamber. I'm done here, done all I can do on this subject.....

 

[Pdvdh]

Maybe I did my math wrong, but I come up with the SAAMI chamber being the longer chamber of the two.
Longer by .013" (.0134) at the NS intersect.
And longer by .011" (.0111) at the start of the shoulder.

From the prints at 4D Reamer Rentals...

Traditional

SAAMI

Without a close review of the information in your prior Post, I will go on to say my math background is stronger than most. Professionally licensed engineer. I ran the math repeatedly before posting in the Shooters' Forum shootout, and my calculation exactly matched the Redding Reloading Equipment website article. Utterly confident. I've underlined and bolded the critical Redding statement in my below 'copy and paste' from their website: https://www.redding-reloading.com/tech-line-a-tips-faqs/133-280-changes

Math performed properly exceeds the credibility of even the finished product (chamber) coming out of a lathe. In the Shooters' Forum shootout, there were some posters that claimed they cut chambers using two different approaches intending to cut the two different chambers, and ended up with the same headspace dimension for both the traditional Ackley and the SAAMI Ackley Improved cartridges. I could only conclude their headspace gauges weren't what they thought they were.

My opinion: Redding has been manufacturing reloading dies for the traditional Ackley, and now the SAAMI Ackley Improved for a long time. Manufacturing a resizing die to the correct headspace is just as critical as manufacturing a rifle chamber to the correct headspace dimension. An error of 0.014" will become obvious in short order. It's a stretch of anyone's imagination to believe Redding could have it wrong, and persist in being wrong, over this length of time.


Here's the 'cut and paste' from Redding Reloading Equipment:
"The SAAMI spec cartridge carries the approved name of "280 Ackley Improved".
The older wildcat has several names including 280 Ackley Improved 40°, 280 Rem Improved 40°, 280 Imp 40°, 280 Ackley, 280 Rem Imp, and more.
The SAAMI spec 280 Ackley Improved chamber is .014 inches shorter at the datum line headspace dimension than the traditionally accepted wildcat chamber spec as previously produced.
Our current production dies are for chambers that are cut to the SAAMI specification and are stamped "280 Ackley Imp".
Any Redding dies made before 2011 are stamped "280 Rem Imp 40°" and are built to the originally accepted wildcat specs.
These older dies will not bump the shoulder of cases for a SAAMI chamber. In other words, the old dies are too deep for the current SAAMI chamber.
Redding makes a Competition shellholder that is .014 deeper than the standard #1 shellholder so the owner of a wildcat chamber can use the current SAAMI spec dies for safe resizing.

Failing to use this shellholder or to back the die away from a standard shellholder by a minimum of 0.014" will result in too much shoulder bump which may create an unsafe, excessive headspace condition when fired in a traditionally dimensioned wildcat chamber."

 

[Pdvdh]

No matter what you conclude about the likeness or difference in headspace dimension between the two differing cartridges, if you want to ensure the factory cases you use can be properly fire-formed without any stretching of the cases at their webs during fireforming, send several of the cases you want to use to the individual you select to chamber your barrel, and insist that they cut your chamber to a slight crush fit against the shoulder of your selected cases when the bolt closes. If this is anything other than the SAAMI specifications, they should not stamp your barrel "280 Ackley Improved", because that would imply the chamber complies with SAAMI chamber specifications. They could be held responsible if the customer is dissatisfied for whatever reason, after-the-fact. Or if a case wall should rupture when fired in that chamber.

So... if you ask them to chamber to the SAAMI 280 Ackley Improved, I expect most gunsmiths will only cut your chamber to match the SAAMI "280 Ackley Improved" headspace dimension (within those chamber headspace tolerances). Those chambers should be able to fire any factory cases headstamped 280 Ackley Improved.

If you require a chamber headspace dimension that falls outside the one and only SAAMI "280 Ackley Improved" headspace specifications, your barrel will almost certainly NOT be marked with the SAAMI "280 Ackley Improved".

 

[DirectDrive]

Redding is using "Datum Line" in their description and the drawings use Neck-Shoulder Intersect dimensions.
So, two different locations mebbe.

And the 4D provided drawings posted above may be wrong.

This is from Lee Precision :
The original 280 Ackley has a neck intersection distance of 2.188" and the SAAMI has a distance of 2.1795" so there is enough clearance in the collet to accommodate the SAAMI cartridge.

Hornady shows the 280 Ackley Traditional NS intersect at 2.180"

Nosler shows the 280 Ackley SAAMI NS intersect at 2.1820"

So dimensions are all over the place for this cartridge.
The -.014 for the SAAMI seems to be widely accepted.
Nosler screwing things up is also widely accepted.

 

[Pdvdh]

Nosler doesn't manufacture reloading dies, so I'd trust Redding or Hornady, companies which both manufacture reloading resizing dies. If they get it wrong, it will eventually cost them money. Best reason in the world for a for-profit business to make sure they're doing it correctly.

Since both the traditional 280 AI and the SAAMI Ackley Improved have the identical 40-degree shoulder, it shouldn't matter what headspace reference length is used when comparing the headspace dimension, as long as the same reference point to measure the headspace on the case shoulder is used in the comparison. I'd like to think the companies would use whatever reference point SAAMI uses, but I'm no expert on SAAMI specifications. Only that once they're established, they're the equivalent of God.

The difference in headspace should indeed be, 0.014" from the cartridge case head to any reference point measured on the case shoulder.

 

[Bob Wright]

This is an interesting read on the subject;

280 Ackley Improved Emperical Headspace Test

Top is SAAMI or Nosler type headspace gauge for 280 AI. Bottom is the “Traditional” headspace gauge for the 280 Ackley Improved, note the difference between the shoulder angles. These C…

gunsmithtalk.wordpress.com

Great article.

 

[DirectDrive]

Great article.

Nice.
I wonder who makes that SAAMI gauge shown in the article, that is shaped more like a cartridge ?

 

[Bob Wright]

PT&G, MANSON and many others grinding reamers do this service.

 

[DirectDrive]

Great article.

I can see now why there's all this controversy swirling around this chambering.
1) The basic prints do not agree from one source to another.
2) Then the Crown Jewel is you have dimensions to the datum line being compared to dimensions to the neck-shoulder intersection.

Guaranteed cluster.

 

[Pdvdh]

PT&G, MANSON and many others grinding reamers do this service.

I highly advise not doing yourself the disservice of ordering a 280 Ackley headspace go-gauge from PT&G. Save yourself the grief. The owner of PT&G was himself, one of the "self annointed experts" on the Shooters' Forum that contributed to the false belief that there was no differnce in the headspace dimension between the traditional and SAAMI cartridge. Do you really want to buy a go-gauge from him? I think he knew full well of the 0.014" difference, but he instead became childish and an embarrassment to himself, in an effort to defend some Forum buddies that stepped in their own doo-doo over their knee high boots.

It was the biggest cluster of technical misinformation from 'experts' I've ever experienced on any Forum. When the dust had finally settled, and the experts were thoroughly embarrassed, the Forum moderator deleted the entire thread. Which was really too bad, because the issue was pretty well resolved - and correctly. But the strain of the embarrassment was evidently more than the moderators could bear. I suspect one or more of their paying sponsers pressured the Forum owner/moderator to delete their mistakes, messes, and childish behavior.

shortgrass has been gunsmithing for decades. Do yourself a favor, follow his advice in post #16, and shop Dave Manson or JGS for a 280 Ackley Improved go-gauge or chamber reamer, if that's what you want to chamber your rifle.

 

[DirectDrive]

I highly advise not doing yourself the disservice of ordering a 280 Ackley headspace go-gauge from PT&G. Save yourself the grief. The owner of PT&G was himself, one of the "self annointed experts" on the Shooters' Forum that contributed to the false belief that there was no differnce in the headspace dimension between the traditional and SAAMI cartridge. Do you really want to buy a go-gauge from him? I think he knew full well of the 0.014" difference, but he instead became childish and an embarrassment to himself, in an effort to defend some Forum buddies that stepped in their own doo-doo over their knee high boots.

It was the biggest cluster of technical misinformation from 'experts' I've ever experienced on any Forum. When the dust had finally settled, and the experts were thoroughly embarrassed, the Forum moderator deleted the entire thread. Which was really too bad, because the issue was pretty well resolved - and correctly. But the strain of the embarrassment was evidently more than the moderators could bear. I suspect one or more of their paying sponsers pressured the Forum owner/moderator to delete their mistakes, messes, and childish behavior.

shortgrass has been gunsmithing for decades. Do yourself a favor, follow his advice in post #16, and shop Dave Manson or JGS for a 280 Ackley Improved go-gauge or chamber reamer, if that's what you want to chamber your rifle.

I've seen the less than favorable reviews of PT&G.
I will say however, that I recently took delivery of a PT&G Rem 700 BDL bottom metal.
Aluminum/black anodized.
Shipping was fast and the bottom metal fit a factory Rem 700 CDL stock with minor fitting that I did with an emery board.

Advice taken on the reamer and gauge.

 

[Pdvdh]

I've seen the less than favorable reviews of PT&G.
I will say however, that I recently took delivery of a PT&G Rem 700 BDL bottom metal.
Aluminum/black anodized.
Shipping was fast and the bottom metal fit a factory Rem 700 CDL stock with minor fitting that I did with an emery board.

Advice taken on the reamer and gauge.

I ordered Rem 700 BDL bottom metal from PT&G once, and did eventually receive it, about 4 months later. No complaints with the quality of it once I finally got it. But it was supposedly in stock when I ordered it. Delay after delay after delay. Multiple conversations with their admin assistant. 4 months later, I received it. Whatever...

 

[DirectDrive]

I ordered Rem 700 BDL bottom metal from PT&G once, and did eventually receive it, about 4 months later. No complaints with the quality of it once I finally got it. But it was supposedly in stock when I ordered it. Delay after delay after delay. Multiple conversations with their admin assistant. 4 months later, I received it. Whatever...

I read that type of review AFTER I placed my order.
I got lucky.