Can someone here set the record straight? I'd like to build a 280AI. However, a few years back, Nosler (and Remington to an extent) upset the apple cart with the SAAMI spec'd reamer.

So the question is:

If the chamber is cut with the original P.O. Ackley design, can factory Nosler 280AI (SAAMI) brass be used in that chamber?

I have been offered the use of a Clymer 280AI reamer and gages. These tools were acquired a few years ago from a closing shop, so I suspect that they are the original Ackley design, not the SAAMI spec'd reamer.

I have an older reamer and have built several barrels with it; I think the new one is .004 or so, shorter. I have not seen or used one though, but, to avoid problems, you should fire form the new brass in your chamber; I always use the "bullet in the rifling" method.
If you are cutting a new chamber it is easier; do not use the old gauges; make the new chamber fit your brass; ie, use the brass as your gauge.

Well. You might email Dave Kiffs people or the people at JGS because I'm not always right. Although I like to belive that I am. LOL

My understanding was that the chambers and ammunition of both cartridges were identical dimensionally. The difference is that the SAMMI gauges simply have the 40 degree shoulder on them like the Ackley cartridge has. As opposed to simply Micky Mousing the headspace with a 280 gauge with it's 17 degree 30 minute shoulder.

It comes back to the old: "glass is half empty, glass is half full." Nothing has changed, they have simply made a propritory gauge for the Ackley, that because of its 40 degree shoulder, can no longer be used to headspace the 280 Remington.

Before the old, how to fire form Ackley cartridges begins. I concur with dpcd 100%. start your loads 4 or 5 grains below minimum and seat your bullets so that they engrave hard into the lands and grooves and fire form them. The long seated bullets will provide your headspacing for you and keep the bases against the bolt face. Then work your loads up after the cases have been formed.

Do not use reduced loads to fireform AI cartridges. Do so and you will end up with excessive head clearance on your formed brass.
The SAAMI spec results in a chamber which is roughly .014" deeper than one cut according to original specs. I say roughly because the measurement to a datum line would vary depending on the neck diameter on the reamer, the radius at the corner of the neck/shoulder juncture, and the precise angle of the shoulder on the gauge.
Careful perusal of Ackley's drawing will show thevariation in specs from caliber to caliber and, in some cases (specifically the 30/06 AI) there are blatant errors.
Generally speaking, one can get away with fire-forming standard 280 in a SAMMI 280 AI chamber but there is a possibility that either short brass or brass with an incipient separation will result. One can lube the brass to ensure proper location of the shoulder but some care must be taken here as well. The lu8be used should have a high flashpoint and kept behind the shoulder. Otherwise there is the potential for dieseling to occur as the air/lube mix is compressed in the shoulder area and pitting of the shoulder area of the chamber can result.
In cutting AI chambers I still use the Juncture of the neck/shoulder measurement minus.006" as my standard.
Nowadays, the best thing for a gunsmith to do is to chamber according to the SAMMI specs and call it good. Once SAAMI has established a standard, that is pretty well what one should work to.
For myself, I would avoid the problem by building a standard 280 and sacrifice the 35 fps gain in performance. Regards, Bill.

quote:

Generally speaking, one can get away with fire-forming standard 280 in a SAMMI 280 AI chamber but there is a possibility that either short brass or brass with an incipient separation will result.

OK, that answers the inverse of the original question.

What about SAAMI 280 brass in an original Ackley chamber (non-SAAMI).

In the end I agree with DPCD. Fireforming brass is the way to go. However, it would be nice to have the correct headstamp on the brass should one travel to a country or countries taht are dead set on a match between firearm caliber marking and ammo markings.

You can always use '06 brass to begin with. Size it in your 280 AI die to create a false shoulder to control headspace and then fireform to blow out the shoulder.

See if this makes sense . . .

280 SAAMI v 280 Ackley

If one takes the time to examine the measurements to the neck juncture, the original Ackley is .014 longer at that point. The same is true for the measurement at the junction of the case and beginning of the 40* taper.

Given these dimensions, it would seem that SAAMI brass (Nosler) could be fired in the original Ackley chamber. That said, .014 of stretch is a lot and could cause problems as noted elsewhere in this thread.

SAMMI brass (Nosler) and the 280 Ackley chamber should be exactly the same. You should be able to fire it no problem. You are simply buying pre fire formed.

See if this helps:


https://gunsmithtalk.wordpress...ical-headspace-test/

Fit your chamber to your brass, or fit your brass to your chamber, and none of this matters.

quote:

Originally posted by dpcd:
Fit your chamber to your brass, or fit your brass to your chamber, and none of this matters.

Yabba Dabba Doo!!! The correct answer.

I recently chambered a Shilen barrel for 280 AI using a Clymer reamer I purchased some 22 years ago.

Used new Nosler 280 Ackley Improved brass.

Nary a problem.

I have the drawings for both new and old, I will retrieve the info from the shop and post later.

quote:

Originally posted by dpcd:
Fit your chamber to your brass, or fit your brass to your chamber, and none of this matters.

This is just fine and is what most people will do when working with any AI but, when a standard is available, it only makes sense to chamber to that standard. As it happens, one is probably safe enough either way but most gunsmiths prefer to work to reasonably close dimensions. The amazing thing to me is that it took months to determine dimensions which anyone with a calculator could establish in five minutes and then the dimensions didn't agree. One can shoot new formed brass in his old AI chamber and it may or may not work fine depending upon the criteria used by the 'smith who did the chambering. I know, for instance, that a rifle chambered according to Ackleys methodology might end up giving excessive clearance with factory brass so many chambered using brass as the gauge and chambered .004 on the brass to give a crush fit. A rifle done this way would likely be close to .010" short on a SAAMI 280 (not AI) gauge so it would be pretty close to the current SAAMI specs for the AI. Regards, Bill.

One of the biggest failings in the gunsmithing industry is that gunsmiths and especially hobbyists, are CHEAP ! 99 times out of 100 the proper tool is out there and can be purchased at a reasonable price and that price built into the job it's needed for. If that tool is not available it can usually be made for under a days labor.

But why spend a buck when you have a hammer, tire iron and a pipe wrench !

No difference. Same deminsions. Just ordered a finisher from Dave Manson.
They no longer sell 280 Ackley Improved. They are now called 280 imp Nosler.

Oldest trick in the book. People had been falling for hundreds of thousands of years and in pops Sir Isaac Newton and lays claim to discovering gravity !

The B A S T A R D !

quote:

Originally posted by MuskegMan:
You can always use '06 brass to begin with. Size it in your 280 AI die to create a false shoulder to control headspace and then fireform to blow out the shoulder.

That's what I do, even in my standard .280 chamber. Simply start with the FL sizer screwed too far out of the press and screw it down a half-turn at a time until your brass can be chambered with just a bit of resistance as the bolt handle is turned down.

'06 brass will be a bit short, but it will grow a little when squeezed down to .284" ID and will grow a bit more when fired. The fired cases will have necks amply long, but will probably never need trimming.

Can the OP explain what benefit is gained with .280AI, in real world terms, over the standard .290 or another 7mm that doesn't have these "SAAMI AI" and "non SAAMI AI' issues?

I all goodwill, and not meant as a troll, I can't see any advantages given the problems the above causes.

Real world benefits of the 280AI? A touch more velocity than the standard 280 Rem. Thought that in itself isn't enough for most to take the jump.

For me, the AI case (regardless of caliber, SAAMI or non-SAAMI) stretches less and therefore cases need trimming less often. Again, not a big issue for the guy that shoots and maybe reloads 20 rnds/yr. I shoot a lot of 22-250 and 223 and every step I can save in the reloading process saves time for more reloading or more shooting. As a result my 220250 and 223 ar AI'd versions.

As pointed out in this thread, there isn't really an issue with the SAAMv non-SAAMI 280AI. It boils down to how the headspace was/is measured when the chamber is cut.
In my case, with the 280AI, I had a perfectly good S/S, cut rifle barrel, chambered in 7mm-08 that I wanted to rechamber. A standard 280 Rem reamer won't clean up a 7mm-08 chamber. So I opted fro the 280AI (which does clean up a 7mm-08 chamber) and 'test the waters'. When rechambered, I wanted to be able to use Nosler brass with the correct headstamp, as well as be able to fireform loads with factory 280 Rem ammo. Hence my question.

That said a few days have passed and the 7mm-08 barrel has been rechambered. Headspace measurement was done with Manson SAAMI spec'd gauges. I'm happy to report that 280AI Nosler brass, 280AI Nosler factory ammo, and standard 280 Rem ammo, all chamber properly.

Is the 280AI the end-all, be-all. No. Will the standard 280 Rem suffice? Yes. But in my case my needs were different and I could, so I did.

I just checked the specs of the two versions of 280 IMP and also the 280 rem



If I read this right, you can use standard 280 Rem cases and the neck will crush fit at the base of the neck the AI chamber or Nosler chamber. In other words the head space is off the base of the neck and so fire forming will be no issue at all.

I have a 280 AI made up here in NZ about 18 years ago & it takes 280 rem brass as a crush fit.

Caution - do not try that with the RCBS version - totally different chamber dimensions and you will need a false shoulder in the case before fire forming.