Just ran across this on another forum and it would explain some things that are going on in my Hart chambered 280AI


Quote:
280 Ackley Improved Alert

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



With Nosler 280AI new cases I have measured .017" headspace with the Hornady headspace gauge and that would explain my primer flattening





on new cases which were with a known load, no pressure signs and have since been reloaded and holding primers fine



If they did this, WHY! For the last 40 years 280AI's have been chambered and now they changed it because Remington had a wild hair!

And the bigger question is Why was there no warning or cautions on the box of Nosler 280AI brass!


Are you guys running across this when chambering for a 280AI?

quote:

Originally posted by woods:
Are you guys running across this when chambering for a 280AI?

This is the first I've heard of a potential problem and I probably do more .280 Ackley Improved chambers a year that any other chamber. I set headspace to a standard 280 gauge minus the crush and use standard 280 ammo to test it. My customers prefer to form their own cases, but now I'll have to get a box and check it out. May have to start issuing a warning, or hand stamp it in the barrel. Maybe someone ought to give SAAMI a heads up. Or, maybe they already have their heads up. A dark place.

Well that makes me feel better malm cause if you don't know about it then it is not well known.

Once the word gets around I suspect Nosler will get a lot less sales of their 280AI cases and rightfully so.

From now on it is 280 rem cases for me.

Wouldn't the manufacturers of the reamers have a line on this?

quote:

Well that makes me feel better malm cause if you don't know about it then it is not well known.

Well, at least in my neighborhood it isn't.

I own a Kenny Jarrett chambered in .280 AI, (which of course he has done hundreds of). Loads were developed specifically for my rifle, by Jarett, using Remington brass. Those loads group well under .5 Moa in a competent shooters hands.

Fire the Nosler factory loads out of the same gun...same results. Sub .5 Moa accuracy in competent hands.

I have shot hundreds of rounds through the gun of both types of ammo and never had a single problem. (Which isn't to say none exist, only that I have not noticed anything unusual.)

JC

BTW,

Here is the original schematic that accompanied the article, (written by Fred Zeglin), that Woods copied and pasted above on this matter.

JC

Thanks Jc

So now we have 2 versions of the 280AI! Like 2 versions of the 6.5x284 that confuses the hell out of everybody except worse in this case.

Brilliant, just f'ing brilliant!

I'll do a search and find the article and maybe find even a smidgen of reason.

quote:

Originally posted by woods:
Thanks Jc

So now we have 2 versions of the 280AI!

Woods,

In reality, there is still only 1 officially recognized .280 AI. That is Nosler's .280AI. Everything else is what it is, Wilcat versions of the .280 Rem. Personally, I think Nosler did a great service by bringing this cartridge out formally. Going forward, as is already becoming the case, when one builds the .280 AI they are much better off just building it to Noslers specs and using Nosler's ammo/brass if this is concern to them.

Heck if I wanted to complain about different versions of the .280 "Improved", I also own a .280 Improved (RCBS), so there are really more than just two versions to complain about.

Seperately, here is the link to the article:
http://gunsmithtalk.wordpress....kley-improved-alert/

JC

Well luckily the SAAMI chambers can be punched the .014 deeper to correct that F U!

quote:

Originally posted by D Humbarger:
Well luckily the SAAMI chambers can be punched the .014 deeper to correct that F U!

To the contrary...doing so is what creates this potential problem/FU!

If your gun is chambered to SAAMI specs to begin with there is no issues at all fire forming your own Remington brass OR shooting Nosler ammo. (The reason why people that are aware of this issue are just chambering their guns to SAAMI specs to begin with if they find this matter to be of any concern.)

JC

Well I guess the genie is out of the bottle but for 50 years there didn't seem to be a problem and now we have one.

On another forum it was posted that the reason is because some of the Remington factory load 280 Remington caliber had variances in the dimension from case head to neck/shoulder of .007". So Remington's poor quality control caused the problem and now Remington has solved it this way. Like putting Barney Frank, Chris Dodd and Chuck Schumer in charge of fixiing FannieMae/FreddieMac! And we get stuck with the results.

From the reamer/headspace gage maker's point of view, SAAMI standardization of the 280 Ackley Improved has created problems. Mostly, it's a matter of making sure folks are informed about the change, proper fireforming--if they want to go this route--and which ammo to use in which chamber.

Ackley's intent, with rimless, shouldered cases, was to headspace the improved chamber so that the un-improved parent cartridge could be loaded and safely fired in it--the parent round was held between the breechface and the neck/ shoulder junction of the improved chamber. He advised that the breech-face-to-neck/shoulder junction in improved chambers be held some.004" to .006" shorter than in the parent chamber. Traditionally we, and other reamer makers, have done this, grinding reamers with a MINIMAL RADIUS at the N/S junction for more positive headspacing during fireforming.

Nosler/SAAMI shortened the traditional 280 AI headspace another .014". Additionally, the radius at the N/S junction was specified at .060" +.025". This was likely done because it's very difficult to form 40-degree shoulders with small radii--they're supplying fully formed ammunition, remember.

What does this mean for the owner of a 280 AI?

First, if you have one headspaced the traditional way, don't buy Nosler ammo unless you want to see evidence of excess headspace and risk case separation--its shoulder location guarantees at least .014" excessive headspace. When you need new cases, fireform them from 280 Remington brass.

Second, if you have a SAAMI-spec chamber, you can buy Nosler ammo OR fireform 280 Remington. The N/S junction on the SAAMI chamber IS .014" closer to the breech face, but the .060" radius at this points provides a little more room to accomodate 280 Rem ammo. You may feel a little resistance as you turn down the bolt handle, but it will go and the case will be held securely during fireforming.

Finally, re-loading. Don't use dies made to the old spec to re-size cases fired in SAAMI-spec chambers. The few re-size dies I checked that were made to the "old" spec would not reach the shoulder of a case fired in the SAAMI chamber.

You CAN use SAAMI-spec dies to re-size cases fired in old-spec chambers, but be sure to set the die so it barely touches the shoulder of the fired case. DO NOT set the die so it bumps the shellholder when the ram is up--you'll introduce excess headspace or crush the case.

There are different versions of the 280 AI out there, so this commentary doesn't apply to everyone. If anyone has questions about his specific rifle, I'm willing to try to answer them.

Dave Manson
1-810-953-0732

Excellent summary Dave, can I copy/paste this as needed and leave your name/number at the bottom?

Hadn't thought about the dies yet. Wonder if the die manufacturers have changed to the SAAMI specs. Right now I am using a combination of Lee Collet (labeled 7MM Express) and Redding Body Die. So the body die would probably not reach the shoulder if I run across a SAAMI chamber and the Lee Collet will leave a little bit of the neck fire formed size which won't hurt a thing.

More than welcome to do that, Woods. I'm not sure where the diemakers are on this, but it's affected them as well.

Dave Manson

All excellent reasons to build a 284 Winchester & avoid the hassle of the 280AI!