280 Ackley Improved Alert

Author’s Note:  Read the post at this link first, it supersedes this discussion.


A few years back Nosler decided to bring the 280 Ackley Improved into their list of custom brass and rifles. In order to do this they wanted to take the 280 AI to SAAMI and have it standardized.

Part of the process of standardizing the cartridge was for Nosler to see if other manufacturers had worked with it. They found that Remington had been chambering the 280 in their custom shop. Now here is where the alert comes in. Remington’s Custom Shop chose to shorten the headspace on the venerable design by .014″. When Nosler sent drawings to SAAMI they picked up that number as well.

So by a vote of the members of SAAMI the commercial established specifications for the 280 Ackley were changed from the original design.  The reason reported for this change is that Remington believed it was necessary in order for factory 280 Remington ammunition to be fireformed safely in an Ackley chamber.  Apparently they did not know that Ackley was the single most successful wildcatter of the 20th century.  While he was not the first guy to create and “improved” design, he was the first to standardize the idea and create a safe method of fireforming factory ammo in improved chambers.

Ackley’s method was simple, he simply used a headspace gauge .004″ shorter than the factory case.  This shorter headspace assured that the cartridge would be held tight between the bolt face and the junction of the neck and shoulder of the chamber during fire forming.  Ackley’s method worked fine for more than 50 years before these alterations to his design were made.

Bottom line for anyone who now works with the 280 Ackley Improved you must decide which version of the chamber you will use; the SAAMI or the Ackley; you cannot safely use the Nosler brass in  a traditional Ackley chamber, although it would still be safe to fire form factory ammo in a SAAMI/Nosler chamber.

Compare the length of these two designs.

UPDATE:  See this post for new information

There is a site devoted to P.O. Ackley and his work:




Filed under Ackley, How To, reloading, wildcat

59 responses to “280 Ackley Improved Alert

  1. I know you put a lot of work into this blog, but it’s been indexed by google and I know people are finding it. When you have time for it again, I’d love to keep reading your stuff.

    Happy Gunsmithing,
    Your friend,

    • reamerrentals

      Understood, Funny you should mention this. I was just thinking I needed to get back at in on a more regular basis.

  2. Pingback: Help! Urgently Need Caliber Advice! - Page 2 - LongRangeHunting Online Magazine

  3. I’ve chambered about ten 280AI’s with a Manson reamer. I ended up not using the headspace gauge I bought from him if the customer planned on shooting Nosler Custom in either 140 or 160 Accubond. I used the cartridge, especially if I was punching a 7mm 08 TC barrel. Although I did just buy a SAAMI gauge from PTG.

    • We have added the SAAMI gage to our stock because of this same issue.
      The word must be getting around because most guys don’t even argue when we ask which gage they want anymore.

      Good Gunsmithing!

      • woods

        I recently used Nosler 280AI brass in my Hart chambered rifle and got flattened primers with a known load. Previously I had used 280 rem brass and fire formed. No pressure signs like brass flow on the case head, excess velocity or hard bolt lift but very flattened primers. Do you think this might have also caused extra thinning of the brass at the pressure ring area? I have reloaded the cases and they are holding primers just fine.

        To me this is unforgiveable and arbitrary in nature. What is the worst part is that there were no advisories or warnings on the Nosler case box.

  4. Pingback: Nosler 280 AI Brass Available! - Page 2 - LongRangeHunting Online Magazine

  5. Pingback: Wildcat Cartridges » Blog Archive » 280 Ackley Improved, something you should know.

  6. Pingback: 280AI question - Page 3 - LongRangeHunting Online Magazine

    • reamerrentals

      The information we have is that all Nosler brass is made to the SAAMI spec. Which makes sense, as they submitted the cartridge for acceptance to SAAMI.

  7. reamerrentals

    It sounds like your chamber was headspaced for the traditional Ackley dimensions. Most likely the reason your primers flattened was because of the excess headspace created by the new brass. When fired the primer backs out to the bolt face, then when the brass stretches to make up the difference, it reseats the primer. This will cause a primer to have a rim formed on it that is larger in diameter than the primer pocket.

    So it could have been high pressure, or it could have been headspace that caused your flattened primers. Hope that helps.

  8. woods

    Well it seems they should have named THEIR new case the “280 Nosler” or “280 Nosler/Remington” or something not “280 Ackley Improved”. If I were a descendant in the Ackley family I would be seeking legal recourse. There must be thousands of rifles and reamers out there that are no longer considered “280 Ackley Improved” according to SAAMI. Of course the genie is out of the bottle now and forever more there will be two 280AI’s. Who decided to let Big Green to influence the process since they have been so successful in decisions in the past like the SAUM’s, 2 positions safeties that don’t always work and setting 280 Remington caliber pressures to work in pumps and autos. I wouldn’t let them decide where I was going to eat lunch. Guess I’m just a little irritated about the whole thing.

    The flattened primers were what caused me to start looking for answers and I found this information. Someone posted on another forum that this happened in conjunction with changes to the dimensions of the 280 Remington case but I have not been able to run that down yet. The 280 Remington case drawings show the distance from the case head to the neck/shoulder junction at 2.199″ and that would mean a .0149″ crush fit at that point with a 280 Remington case in a 280 Ackley Improved (SAAMI) chamber. That seems like more than necessary and may cause a do-nut.

    Guess I will switch to Norma 280 Remington cases.

    • reamerrentals

      No changes have been made to the .280 Remington. Your dimensions sound pretty close to what I remember from our research. That is why we put out the 280 Ackley Improved Alert to begin with. It creates just enough excess headspace in the brass to cause problems. An new shooter with little experience would have no way of knowing what was wrong.

  9. Pingback: 280AI trim length - LongRangeHunting Online Magazine

  10. Randy Perkins

    This is great info. My question is this; does Kimber use the SAAMI headspace in their rifle or the original 280AI headspace? Refereing to the 84L

    • Spike Heape

      Randy, yours is the question I would love someone to answer. As far as I know only Kimber and Nosler are making the 280 AI in factory rifle. I am looking to buy one or the other. Do the use the SAAMI headspace or the original.

    • reamerrentals

      Just talked to the people at Kimber. They confirm that the specifications they used were for the Nosler (SAAMI) brass. So factory chambered Kimber rifles in 280 Ackley Improved are indeed SAAMI spec.

      I want to make clear here again, the difference is not in the reamer. The difference is in the headspace gauges. Nosler Brass is shorter than a “Traditional” 280 AI chamber.

      • Spike Heape

        Randy, thanks so much, my wife is going to buy me either the Kimber or the Nosler rifle for christmas, I’m leaning towards the Nosler. thanks Spike

  11. Well, I’m not sure about all this after I just chambered my 6th 280AI chamber. I had on hand a GO gauge for the std 280 chamber as well as new Nosler AI brass, new Nosler 280 std brass and new RP brass. I can detect NO difference in headspace between a chamber cut to .004 short using the GO gauge as a NOGO and by checking the chamber with new Nosler 280AI brass, Nosler 280 brass and new 280 RP brass, I get the same resistance on all brass.

    • reamerrentals

      I had on hand a GO gauge for the std 280 chamber as well as new Nosler AI brass, new Nosler 280 std brass and new RP brass. I can detect NO difference in headspace between a chamber cut to .004 short using the GO gauge as a NOGO and by checking the chamber with new Nosler 280AI brass, Nosler 280 brass and new 280 RP brass, I get the same resistance on all brass.

      First I want to congratulate you on knowing that the standard 280 Remington is the No-Go for the Ackley chamber! If anyone has a question on this check out this article: http://wildcatintel.com/blog/?p=109

      The reason you feel no difference is simple. Using the gage to set headspace as you did creates a “traditional” Ackley chamber. So it does crush the neck shoulder junction of standard 280 Remington brass .004″. Where the confusion comes in is with the Nosler brass. Nosler brass is .014″ shorter at the formed 40 degree shoulder than the Traditional Ackley chambering when formed.

      So, because the Nosler brass is formed to the body and shoulder of the improved case you are feeling what is called an “interference fit” the equivilent of a tapered pin in a tappered hole. The forward motion of the case is limited a little by the shoulder having alreacy been formed by the brass maker (Nosler). However there is nothing to stop the case from moving forward when the bolt is closed.

      I know one gun writer who has been working with the same issues you brining up. He found that if he necked his brass up to 30 caliber and then back to 7mm(284) there was a noticable shoulder left when the case engaged the shoulder of the chamber.

      This is a known issue, that is why the reamer makers make a seperate gage for the Nosler brass, normally ordered as SAAMI. It’s a good idea to get both the go and no-go in the SAAMI configuration because they have a 40 degree shoulder. Unlike the “traditional” Ackley gages.

  12. Pingback: Changing 280 rem to a 280ai - LongRangeHunting Online Magazine

  13. Walkinhorseman

    I am currently on my third 280 Rem chambered rifle. The first was a Sako L61R rebarreled with a Douglas and Clymer Reamer. The second was a M70 rebarreled the same. My current rifle is a factory Sako AV. I never wanted to play around with case forming. I got to this post because I am considering the Nosler rifle but due to this debacle, I won’t select the 280 AI. I was trying to decide between the 7mm Rem Mag and the 280 AI, in fact, I am now leaning to the H-S Precision rifle in lieu of the Nosler. Nosler should have been more responsible and pushed back on Remington and SAAMI. It would have given nre life to a lot of great old guns in the correct Ackley chamber. I wonder how Kenny Jarrett would weigh in on this issue. The 280 AI is one of his pets.

    • You would have no problem if you used a Nosler Chambered rifle with Nosler brass. They are a match.

      In terms of ballistics there is very little difference between the two versions. The brass is just not interchangeable.

  14. Hanz

    The real problem I see is that everyone involved has opened themselves up to the liability that there ammo will fit in everyones guns but With a headspace problem. Not a good idea for some “smart” gun guys?

  15. Richard Nelson

    The rifle I recently chambered has been fired many times and took a nice buck a couple weeks ago.

    I have measured the Nosler 280AI brass before and after firing and can detect no difference in the position of the shoulder or the neck/shoulder juncture. A simple neck size and they are ready to load.

    • reamerrentals


      That indicates that your gunsmith used the SAAMI gauges. If he new you were going to use Nosler brass then he wisely used the correct tools for the job.
      In today’s market I would simply mark any barrel I chamber for 280 AI as Noler or Traditional.

  16. Walkinhorseman

    Thanks Fred. I understand that. Gunsmiths and experienced reloaders can keep things sorted out and deal with the problem. My point is, that should not be necessary if Remington and Nosler had not been self serving. Nosler is supplying high quality brass that would be welcomed by those who have the old Ackley standard chamber, but that is not a practical option. The other point that I haven’t seen anyone make here yet, is reloading dies. I really like my Redding 3-die sets. No matter how good the Nosler brass is, eventually it will have to be full length resized. Redding catalogues the 40 degree dies but how would you use the full length die if it is the Ackley standard chamber headspace? I guess you have to turn 0.014″ off of the FL die or the top of the shell holder? Will the die companies offer both SAAMI and Ackley standard dies? As Woods points out, the cartridge should have been renamed to make it unique and call out the distinction.

    • reamerrentals

      Walkinhorseman, I know from research that this was an accidental change. Computer design work caused the problem. I don’t ascribe any purposeful acts by either Remington or Nosler here. The real problem is that they have engineers making decisions about cartridge design. There are many experts, who make a living with cartridges, that could have been consulted to assure that they had the correct dimensions.

      Some sources implied that the 280 Ackley Improved was not one of Ackley’s designs. I have proof that it was, in a letter from P.O. to Bevan King he specifies a .455” diameter shoulder with a 40 degree angle. Ackley also indicates the headspace method was identical to his other improved designs. Much like the 270 Winchester Ackley stated concerning the 280 AI, “Anything done to increase the capacity is going in the wrong direction. So I only make these chambers on the insistence of a customer who thinks he mush have it.”

      I think it’s funny that they chose a cartridge that Ackley did not promote as one for their line. On the other hand, it has been among the most popular of Improved cartridges for many years, so it had built in sales appeal.

  17. PC

    I wonder what version my TC Encore factory 280 AI barrel is? I will call them and see if they can shed some light.

    • reamerrentals

      I would expect all manufacturers who produce guns in this caliber to make them to match the SAAMI spec. This way the lawyers can point to ANSI standards and say they followed them. Custom gunsmiths get to make up their own mind. We now mark all guns we chamber in 280 Ackley as either Traditional, or Nosler depending on the clients choice.

  18. It’s obvious Nosler wants you to be stuck using their brass only. These big companies are always trying to pull something on the public. This one is going to backfire on them as in a law suit.

  19. John Fuquay

    Just wondering, with all that’s been said, if this is correct: 280 Remington brass may be fire formed in either a Kimber or a traditional chamber — and the result will be safe but not interchangeable cases? So, the owner of a Kimber could buy virgin Nosler brass, the the owner of a traditional AI must fire form. I would find it hard to believe any discernible difference in ballistics or accuracy as long as the brass matches the chamber. Am I right?

  20. Walkinhorseman

    From the Redding Reloading website Tech Tips:

    “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.

    To find the die part numbers for a current production SAAMI spec. rifle, please download our current catalog as a .pdf from http://www.redding-reloading.com.
    You will find these dies listed in Series C and Category II. Limited quantities of the traditional wildcat dies which are marked ” 280 Rem Imp 40° ” are available at Custom Series Die prices.

    Bottom line, don’t rely on only the web.
    The names many list for this cartridge can be misleading.
    Remember, they are wildcat cartridges and adhere to no formal standard.

    Note: Any dies that Redding makes for SAAMI approved cartridges are always stamped with the SAAMI approved name or abbreviation.”

    • reamerrentals

      This is great input. As a preliminary announcement I am preparing a video to go over the latest data regarding this discussion. Some surprising developments have arisen and a video seemed the best way to display the information. I want to clarify and clean up many misunderstandings that have been created by the conversion of the 280 Ackley Improved to a SAAMI cartridge. Watch for this update to appear very soon.


      • Layne

        I am tuning in a bit late with a question. The .280 Improved cartridge often credited to P.O. Ackley is a wildcat and since (as far as I know) the chamber dimensions of wildcat cartridges are not standardized, on what did you base your comment about the Ackley chamber being .014 inch longer than the SAAMI chamber? Are the Ackly chamber dimensions standard among all makers of chamber reamers and headspace gauge?


      • reamerrentals

        This information comes from the two drawings provided for chamber reamers by PTG. I have since gathered the actual SAAMI drawing for the Nosler version of the 280 Ackley Improved. And as stated in a recent comment will be publish a full update soon. I am currently trying to lay my hands on some Nosler brass to finalize the full report.

        While normally SAAMI does not “standardize” wildcats in the case of the 280 Ackley Improved Nosler submitted this cartridge for approval, and it is a SAAMI cartridge. As for the idea that P.O. Ackley did not publish standards this is a long standing fallacy. He published over and over again the methodology for headspacing his designs. Now the 280 AI is not a true Ackley cartridge in that he did not make this cartridge as far as records can establish.

        The confusion over headspace on this cartridge is a result of Engineering drawings and CNC Software. All to be explained in the update to follow.

  21. dhaidak

    the guys at hsd precision told me they use the nosler/saami version

  22. Pingback: 280AI Custom Ammo Alert - LongRangeHunting Online Magazine

  23. Brooks

    Does anyone know which chamber Cooper uses for their 280 AI chambered rifles?

    • Cooper states they use the SAAMI / Nosler gauge. If you look the video posted directly above this post you will see that it makes no difference at all. This is really just a math problem caused my an engineer… in the end they are the same.

  24. Brooks

    Thanks reamerrentals

  25. I have an older 40 degree chamber and I purchased some Nosler brass… I haven’t loaded it yet and just stumbled on this blog…. It seems to me that if I seat my bullets long so they engage the rifling for the first firing the case will fireform itself… Any thoughts on this. I know i’m back to fireforming but at least I can get the benefits of hopefully higher quality brass than the fireformed ww .280 brass I have always used.

    • Bob

      The way I discovered this problem between traditional and new SAAMI dimensions was to fire Nosler 280AI brass in a traditional chamber. If your chamber is similar dimensions to mine, your primers will be severely flattened. That happens because the case moves too far forward in the chamber and the primer backs out and reseats and is flattened.

      IMO seating against the lands will not prevent this. When the primer fires it will push the case forward in the chamber with enough force to seat the bullets deeper and the forward movement will not stop until the shoulder stops it.

      But, other than the primer being flattened and a little more case thinning at the pressure ring, there would be no effects that will prevent you from reloading those Nosler 280AI cases that have been formed to your chamber. Size to headspace on the shoulder with minimal setback and those cases should last a number of shots. Many (if not all) belted cases have greater than .017″ case stretch to reach shoulder contact and are reloaded. Your Nosler 280AI cases may shorten more than regular 280 Rem cases but again that is not prohibitive.


      • Bob, as with my comments to Brian: based on the actual tests performed with the correct headspace gauges for both traditional and Nosler 280 Ackley Improved chambers, there should be no difference in headspace. If there is, your chamber is out of spec.

        With that said, if you choose to keep your chamber and just fire form to match it, then your comments are right on target.

        The Nosler brass should shorten up much less than the 280 Remington brass because the Nosler brass is already “improved” so there is much less pulling back when it is fired the first time. As apposed to the fire forming of factory 280 brass in an “improved” chamber.

        Here is the second article on the 280 showing the headspace tests: http://bit.ly/PthvXx

    • Brian,

      A few thoughts come to mind. First there is a second article on this blog about the 280 AI that involves a test using the correct gauges to empirically test the two chambers head to head. If you experience headspace problems with either 280 Remington brass or the 280 Nosler Ackley Improved brass then your chamber is probably out of spec.

      Scroll up to the video just above this comment, it shows the test mentioned in the paragraph above.

      I would recommend using gauges to see if your chamber is correct. Unfortunately many gunsmiths do not bother to get the correct gauges when chambering for Ackley cartridges. There seems to be confusion over the proper methods to headspace these simple cartridges. Gauges are readily available so there is no reason to guess. I know of one instructor at a gunsmith school who still teaches the process wrong even after being told he is incorrect.

      You could utilize a fire forming process such as you described. If you do be sure to drop back to starting loads because having the bullet jammed into the rifling will raise chamber pressures. Keep in mind if you do so, you really do not have a 280 AI, because it is not correctly headspaced.

  26. Harold Calvert

    I just purchased a Cooper 280AI. I spoke to Cooper twice to verify the type of chamber. They said they make their rifles with the traditional AI chamber. The dies they use for loading their test ammo is the traditional 280 rem imp 40 FL die (#56266) from RCBS.

  27. Morgan

    Great thread of info, I have two rifles in 280 AI that were chambered before Nosler set their dimensions for their brass. After buying two boxes of Nosler brass to save time I now see why I have been having issues with the head space. If I buy the Nosler 280 Rem brass can I fireform it to my chamber with no probloems? The Nosler cases just seemed to be of higher quality than the Rem brass I normally use.

    • Bob

      You can buy Nosler 280 Remington caliber brass and it will work fine. That is what I do with my 280AI. Any manufacturers 280 Remington caliber brass should work the way Ackley intended in your chamber without the excess headspace issue that you and I both evidently have with the Nosler 280 AI brass

      • reamerrentals

        Again, in this case it is likely that your gun has excess headspace as compared to the proper Ackley dimensions. That does not mean you cannot fire form brass to work, only that your cases are probably a few thousandths longer than Ackley spec.

    • reamerrentals

      Most Likely if your having trouble it’s because not all gunmakers follow Ackley’s headspace rules. I have been amazed how much confusion there is over this subject considering Ackley published the information in his books, going on 50 years ago.

      You should have little trouble reworking the brass to work in your chambers. Your best bet is to neck up to 30 caliber and then resize the neck to 7mm purposely makeing sure to headspace tight to the chamber.

  28. Pingback: 280 Remington mountain rifle - LongRangeHunting Online Magazine

  29. Pingback: 280 ack imp 40 degrees vs Nosler brass - Page 2 - Long Range Hunting Online Magazine

  30. reamerrentals

    Ran onto this article and thought I should link to it to keep the thread as complete as possible.

    At the end of the article Simpson quotes Dave Kiff to support his position. However, Dave provided all the drawings to me for this blog and is the maker for most of the gauges we own for both the SAAMI and Traditional headspace. The confusion goes on.


  31. Pingback: Semi Custom Kimber Montana 280AI - Page 4 - Long Range Hunting Online Magazine

  32. Pingback: .280 AI SAAMI questions

  33. Jim

    I’ve fired Nosler Custom 280 AI in my TC Pro Hunter barrel with no problems. I have form 280 AI from Remington and Hornady 280 brass with a low to mid range IMR 4895 powder charge and the bullets loaded to touch the lands and grooves per the Nosler Loading manual suggestion. The fire formed cases work fine and I’m on my 8th and 9th loading of the fire formed brass. Yes, I annealed them after the 4th firing.

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