There was a post regarding the 40 degree improved vs. new SAAMI dies, but damned if I can find it. What was all the hub-bub? Thinking about picking up one of these...

thanks.

Here ya go. Originally ackley spec for mine.

http://gunsmithtalk.wordpress.com/2010/01/13/280-ackley-improved-alert/

Great link, MallardAddict, I've got a new Kimber 84L Montana chambered to the 280AI, and had questions as well. This link answered all my questions. So, if I use Nosler brass and/or factory ammo using Nosler brass from CorBon or Nosler, I'm good to go. Also explains which Redding dies to get. Thanks!

You can also fireform regular 280 brass from what the article says. I wonder if it has a bit of "crush" as is suggested when forming cases?

Came across this on NoslerReloading.com. Didn't even know the site was out there...

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

The Kimber 280 AI seems snake bit from what I read here:

"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."

As I understand, the Kimber 280AI chamber is SAAMI spec. Thus, I don't understand why you say the Kimber is snake bit. The line you quoted refers to rifles chambered to the original wildcat specs.

Yes the Kimber chamber is SAAMI spec.

Any manufacturer who chambers for the 280AI will use the SAAMI spec because SAAMI standardized the .280AI dimensions whereas the wildcat chambers can and do vary considerably.

Golly gee, imagine that. It'll have a chamber to match the bore, [bleep] up as two boys kissin'.

I think there's a few more Montana threads that you could go try to dump on, you're kinda' slacking. Please try harder sir.

WTF??? Possibly the most Assinine thing you have ever posted. As stated above the Montana .280ai is to SAAMI spec so the Nosler brass is actually factory brass designed to fit it without fire forming.

Have you actually handled a Montana .280ai let alone shot one? I have plenty of trigger time on my buddies. It along with the 2 Montana's I currently own have all shot MOA and typically better with minimal load work up.

Looks like Reddings #78428 is the place to be. What loads are your buds running? Any luck with 162's?

Comparing the Montana in a 7mm WSM to the 280AI the WSM specs show a weight of 6# 3oz and the 280AI weighs 5# 10oz. Thats over a half pound difference.

I might consider a 84L but I have other rifles and a 84M that must weigh less than the 84L.

The 8400 Montana in a WSM weighs less than a M70 Featherweight did.

So many rifles. Great to have the choices to consider.

http://www.kimberamerica.com/rifles/model-84l/montana

The 8400 action isn't slim and trim like the 84's.

Yes that has to be the case. I have some 84M's now and a couple of WSM's.

It's fun thinking about all the combinations.

The 280AI would reach as far as I would shoot at a deer I suppose however during the off season if I see a coyote well then ...........

I said I would buy a Kimber 84L if they offered it in 280AI but now I am buying another type of rifle.

I'll do that, I must've missed 'em. The boys from Yonkers deserve to eat dog food.

What kinda luck are you having with yours?

A solid six-minute shooter. The bore looks like the Rubicon Trail. They knew it when they shipped the [bleep] out the door.

280AI?

16bore, if you look at the Nosler #5, and the Nosler #6, the diagrams are different.

Let me know if you buy that Kimber, I have fireformed brass and dies.

You mean this?


Did you give up on yours??

yeah, those are the drawings i was referring to. Some of the info I have read on the SAAMI version is conflicting. I have read Nosler shortened it for SAAMI, like the version on the left. Their latest manual show the version on the right though???

I have not given up per say, just got tired of dicking with it. I would rather just shoot a normal 280 or jump to a 7 mag. The AI certainly performed speedwise, but fireforming gets old. I am building a 6.5-06...