Hoping someone can clear this up for me, as my head's going to explode.

I have a friend that took his bone-stock 280 Rem to a gunsmith and asked for it to become a 280 Ackley. The 'smith turned the barrel back one revolution and chambered it (with POA's original .004" crush fit on the datum line shared by both the regular and Ackley forms of the 280).

Will this work--without excessive headspace--with SAAMI 280 Ackley brass, e.g., Nosler?

From what I'm surmising within this Nosler FAQ (which the gunsmith seemed to follow to a "T"), is that the issue is when a 280 Rem is rechambered to an Improved without first turning back the barrel.

Any & all help greatly appreciated.

The correct chambering for the original is not a .004" crush on the datum line but a .004" crush at the juncture of neck and shoulder. It is readily apparent that this measurement can vary with differences in neck diameter and shoulder angle. GD

Yes it will work.

They had it set up the way P.O set it up.

Will work with standard 280 loads/brass as well.

My mistake.

What greydog said.

You don't know if it will work unless you chamber some UNFIRED .280 factory brass. There isn't a vast amount of difference in the Nosler and Ackley chambers, so SOME factory .280 brass will work fine--and some might not.

I emphasize UNFIRED because there can be problems with some fired cases, due to them lacking the slight radius between the neck and shoulder.

John, just to be clear, standard 280 Rem or improved new brass, e.g., Nosler?

Either one.

In general, having messed around with quite a few .280s and .280 AIs, I prefer a little chambering resistance in an AI chamber with any kind of .280 brass.

I am curious, though, how the variance occurs in the first place. The Nosler FAQ implies it has to do with rechambering a standard 280 Rem without turning the barrel back, creating what several say is between .010"-.014" of headspace. Is this the generally accepted rationale?

From my understanding it is largely a difference in measuring the cases from the datum line vs the shoulder junction. I have not shot the Nosler brass in my AI but I would assume that if it has a crush fit it would be fine, if not jam the bullets to fire form. If you are really concerned then neck up and create a false shoulder.

The rifles I chambered with a $37 sammi 280AI go gauge from PTG play well with Nosler 280AI brass.

I quote Dave Manson:

"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

**********************************************************************************************************************************************************************************************
Additionally, I add that Redding current production dies are for chambers that are cut to the SAAMI specification are 0.014 shorter in headspace than the original PO Ackley specs and are stamped "280 Ackley Imp". Redding dies made before 2011 are stamped " 280 Rem Imp 40° " and are built to the originally accepted PO Ackley specs. RCBS also has two different dies: Group D 17001 .280 Ackley Improved and Group A 17030 .280 Ackley Imp (Nosler)

Sugar coat all you want, but Nosler created a cartridge with different specs - 14 thousandths is 14 thousandths - or as this say, "It is what it is."

This explains and clarifies what I was asking on the reloading page last week. Thanks for posting it.

RM

The information from Dave Manson is interesting--partly because the difference in headspace is so small--which can result in something I personally experienced when Nosler first introduced the .280 AI as a factory round.

To promote the "new" cartridge they decided to take a couple of gun writers on a pronghorn hunt in Wyoming, one of them me. Nosler wasn't building rifles then, so I had a Ruger No. 1 chambered for a smaller 7mm round rechambered by a local smith. But there weren't any headspace gauges available, so I took him some unfired Nosler cases--which at the time were headstamped "Norma." He used a .270 Winchester Ackley Improved reamer and a 7mm neck reamer to do the job.

The rifle shot very well with both the factory ammo Nosler sent me (which was loaded by Norma, in the same headstamped brass), and with various handloads. But I also had some .280 Remington ammo on hand from various projects, and decided to see how it would fireform in the new chamber. It formed fine, without a hint of excess stretching.

Thanks for the info on the 280 Ackley. guys. I have a Savage 110 Hunter in 280 Ackley Improved. I bought Remington brand 280 Remington brass and have been fireforming it to get 280 Ackley brass. My rifle's bolt closes snug on this factory brass, which leads me to believe my rifle isn't chambered for the Nosler version, 14/1,000" shorter. Am I right? I guess I shouldn't buy any Nosler 280 AI brass.

Dunno--but do know that .014" is just slightly more than the thickness of the average business card. Have measured to the datum line on a bunch of factory brass, and it can easily vary that much.

So there still are two versions of the 280AI - wonderful.

That is how I check an AI to see if it's done right slight resistance with a factory round. Had several that were not done right,

"Slight resistance" is exactly what I found with my rifle, chambered using Nosler/Norma unfired brass, with unfired Remington factory .280 brass.

That said, after some experience with several "improved" rounds, mostly 40-degree Ackleys in cartridges from .223 Remington to .35 Whelen, fired "unimproved" brass in the same chamber often won't even go band, due to the lack of the little shoulder/neck radius on new brass.

My point is that .014" difference in headspace (IF the .280 AI chamber is reamed that accurately) is a very tiny amount--and a very slight amount of variation in both the chamber and brass can work just fine, whether the chamber is supposedly "original" Ackley Improved or Nosler.

Should also add that the standard allowable SAAMI variation in headspace for most rifle cartridges is plus or minus .007"--exactly half of the difference between the "Ackley" .290 AI and the "Nosler .280 AI." Again, this is typical rifle-loony obsessive minutiae.

Yet another point: Most mass-produced full-length sizing dies tend to size brass to different slightly different headspace when using the standard "screw 'em in until the die contacts the shellholder" directions. This generally varies as much as the headspace difference between the Ackley/Nosler .280 AI rounds, especially when we throw in the differences in individual shellholders and presses.

I'm quick to mention die setup any time I'm talking with a newbie handloader.

Put a Nosler SAAMI 280 AI in the original Ackley and it's loose and rattles - is that minutia?

Sorry, this is sore subject with me - these days anyone can take someone else's non-SAAMI design, change it around a little and "hijack" it as their own to SAAMI. I've heard all the "reasoning" behind Nosler's decision, and I still don't think there was a legitimate reason to change the original Ackley dimensions.

Put a minimum SAAMI-spec ,30-06 round in a maximum SAAMI-spec .30-06 chamber, and the "loose" headspace is exactly the same as the difference between the Ackley and Nosler .280 AI rounds.

Yes, I understand what you're saying, but in my experience it isn't the end of civilization as we know it.

John:

I don't want to hijack this thread, but this question is related. Just about everything I read says that the .280 is downloaded, or at least has a lower SAAMI-spec PSI limit, than the AI. I've also read that if the .280 is loaded to the same pressure limit as the AI, i.e., 65k, that there really isn't very much gained by going the AI route. So here's my question: You have a nice target-velocity schedule, based on bullet weight, for the 7x57 since that data has historically been all over the board. Do you have something similar for the .280? In other words, how much velocity should one expect by loading the .280 to the same AI pressure level?

I don't know if what I'm asking makes any sense, but there it is.

Thanks

I just did a bit of figuring with Hodgdon's 280 data for a 140 grain Partition.

H4350 is reported in CUP, so I extrapolated to 54000 CUP which is a usual pressure for 300 Weatherby. This gave an estimate of 3054 fps for the extrapolated max in the 280.

A similar calc for IMR4451 at 65000 PSI estimates 3059 fps.

Of course grain of salt and Danger Will Robinson, yadda yadda.

Glad you asked that question. I was just thinking about the same thing.

Mule Deer:

Just out of curiosity, how much of a velocity difference did you find with the .280 AI over the standard .280?

I've only ever owned two rifles chambered for an "improved" cartridge. The first was a .218 Mashburn Bee, the second (which I still have) a .219 Improved Zipper. Both of the parent cartridges for those are quite tapered and the improved versions show a marked increase in case capacity.

I own a .280 (a Remington Model 725 - which I think to be perhaps the handsomest regular production rifle Remington ever produced, but that's just an opinion and worth whatever someone will pay for it) and I don't see that there's much room for increasing case capacity by blowing out a .280.

Thanks.

Rem

According to one basic rule of internal ballistics, loading the standard .280 (SAAMI Maximum Average Pressure of 60,000 PSI) to 65,000 PSI (AAMI MAP for the Nosler .280 AI) will gain around 60-65 fps in velocity with loads in the 3000 fps range.

The .280's gain in powder capacity over the standard .280 isn't all that much, about 4 grains, which according to another rule, means a similar gain in velocity when loaded to the same pressure. So about half the .280 AI's gain comes from the higher pressure. Add the powder capacity to the pressure and the AI's gain is around 120-130 fps, in an equal-length barrel.

My first .280 was a custom rifle made by the late Dave Gentry, and I handloaded it warmer than the SAAMI specs, using both the old "pressure signs" familiar to most handloaders, and a computation of what should be possible when loaded to .270 Winchester pressures (also a 65,000 SAAMI MAP). It had a 23" barrel, and at first I used two different loads that shot to the same place, a "deer" load with the 139 Hornady Spire Point at around 3100 fps, and the 160 Nosler Partition at around 2900. The Hornady load shot very well, but the Partition load wasn't quite so accurate, though it killed everything I pointed it at, including one of my two biggest caribou bulls, shot at just under 400 yards. The first shot landed in the right place, but the bull (as caribou sometimes do) locked up and stood there, so I shot again. The second landed within two inches of the first, and the bull fell over. So it didn't really matter that the 160 didn't shoot quite as well as the 139.

I eventually was reminded by the late Chub Eastman, who worked as the writer-relations guy at Nosler for many years, that Nosler also made a 150-grain Partition, which in his experience tended to shoot better. Eventually I settled on it as an all-around load at just about 3000 fps, which shot and worked great. Of course, that was back before super-high BC bullets became absolutely necessary for killing big game.

Have owned two other .280s, and three .280 AIs, and never could tell any difference in killing power or accuracy between them, given the same bullets--these days often with much higher BCs. But then I always handloaded the standard .280 to what was probably around 65,000 PSI.

BTW, if you have an "old" chamber and "new" (SAAMI) FL sizing die, Redding makes one of their "Competition" shellholders which is +.014" (to prevent pushing the shoulder back that .014" with die body touching the shellholder). This can obviously also be achieved by backing out the die as mentioned previously.

This Nosler FAQ from 2013 confused me. Based on the first paragraph, I got myself halfway believing a rifle set back a thread and chambered would meet the SAAMI standard. Called Nosler and they said "Nope. .014" headspace." They're right; proved it today on the rifle I mentioned at the beginning--shuts on a SAAMI-standard no-go gauge.

That said, I think this FAQ could be a little clearer......

Good timing... I just purchased a barrel chambered in 280 RCBS with dies marked 280 Improved 30 deg.

It's a shouldered barrel I need to install on a Rem 700 LA. How would i go about head spacing it correctly? also, can I fire form 280 Rem brass with it then reload with the dies?


Thanks

Not answering your questions, but do you have fired cases from it? A friend has a 1937 M70 Super Grade with "7mm" marked on the barrel. It was originally a 7x57 but had been wildcatted probably in the 50's or 60's. Our best guess based on a lot of research was 7-06 RCBS Improved (30 deg shoulder). If you're not positive, consider doing a chamber mold with Cerrosafe, etc. https://www.brownells.com/gunsmith-...osafe-chamber-casting-alloy-prod384.aspx

I do not have any from the previous owner. I'll check out the mold idea. Thanks

If, when you chamber a 280 cartridge, you can feel some slight resistance, it is perfect. If there is any clearance, it is not. It may be that factory 280AI will headspace at the corner of the shoulder quite well since the outside corner of the shoulder is further forward on a 40 degree than on a 30. GD

Getting back to the question of using Nosler factory brass in an 280 Rem Ack. Imp. 40 degree (pre SAAMI chamber). In an adundance of caution I always size new Nosler factory brass up to .308 cal. and size back down to .284 cal. leaving a false shoulder. This results in a loaded round that gives slight but noticeable resistance when closing the bolt. I have never experienced and problems with excessive headspace using this method. It adds a couple of steps to the process but gives me confidence that my loaded rounds are safe. I use Redding dies marked 280 Rem. Ack. Imp. 40 degree which were made around 1993. I have never fired Nosler 280 Ack. Imp. factory rounds in either of my rifles so I cannot comment on how that works.

I've never used factory brass in this chambering.
I have both RCBS .280 Remington Dies and RCBS .280 Rem IMP 40 dies.
I start with once fired .30/06 brass, resize with the standard 280 dies to create the false shoulder and then load seat using the IMP dies thereafter. Never had an issue.

My rifle is a Winchester Featherweight XTR in 7x57 which was re-chambered to the Ackley chambering. It is a nice hunting rifle and quite the looker. Best performance from the 22" barrel comes from 140 grain bullets which reach 3200fps with relative ease. Lighter bullets suffer from the shorter barrel and the 175's will hover in the 2800-2850fps range,

Probly always will be.