280 AI: SAAMI chamber or not???

F

FLChinook

New member
I was all ready to get a 280 AI when I discovered the controversy started when Nosler got the SAAMI standard for the cartridge changed from what it had been for years. My eyeballs are almost worn out from viewing comments on this.

Cooper Firearms has not changed their 280 AI chambering to accommodate the SAAMI standard and they say they have no plans to do so. They say their 280 AI's work fine with the latest Nosler 280 AI ammo (although they didn't initially; apparently, the first Nosler primer pockets were deeper than they are now and the extra headspace allowed the firing pin to push the cartridge into the chamber which interfered with a good strike).

Nosler, of course, has adopted the SAAMI standard for their 280 AI rifles.

With the old chambering, the cartridge length is the same as 280 so fire forming brass would not be an issue. I don't know if you could chamber a 280 round in a new (Nosler) 280 AI SAAMI rifle... although I suspect you could...

So the question is, if I'm bound and determined to get a 280 AI (and not a 280 which will not chamber a 280 AI round), should I get one with the new SAAMI chamber (ala Nosler) or with the original AI chamber (ala Cooper)???

Why does life have to be so complicated.....:D
 
Listen. I've studied this.

They are one and the same!!!!!

The Nosler / SAAMI chamber is the exact same chamber as the old "40 degree Ackley Improved".

The no-go gauges are shaped differently, but the actual chambers / reamers are the same, with the same shoulder angle of 40 deg. The no-go guage doesn't "fill up" the chamber on the old AI like the new Nosler, but it correctly places the shoulder and tells you when to stop reaming. The only purpose of the no-go gauge was to touch the chamber shoulder at the right time - the weird / plain shape that does that and ONLY that - touching the chamber's shoulder at just one point exactly, which is sufficient to tell you to stop reaming, is what started this controversy (the fact that Nosler made a no-go guage that fit precisely).

https://www.youtube.com/watch?v=Vlskn2CE7-Y

No controversy. No problem. Headspace exactly the same.

So you can fireform in either chamber just fine and dandy.

So mix and match and shoot and be happy! :)
 
I've seen this video and taken comfort in it but it still doesn't compute in my engineer's brain. The SAAMI web site gives the dimensions of their cartridge and there are definite differences between those and the dimensions of the "old tried and true" cartridge.

I've never used a No-Go gauge and don't know how they work. It just seems if you have a reamer that gives a SAAMI chamber and another reamer that gives a OT&T chamber, they will not be the same...

What am I doing wrong??
 
I am going to attempt to explain this. The difference is in the gauges, not the reamer.

The Nosler gauge is shaped exactly like the cartridge. It has a shoulder and sides that contact the chamber walls.
The traditional gauge is a straight cylinder that is tapered at the end to match the shoulder of the cartridge. It is not as large in diameter as the cartridge body, but its length is precisely matched where the neck becomes the shoulder of the cartridge. To put it another way, you can take the Nosler gauge and turn it on a lathe and cut the body of the cartridge off to create a traditional gauge.

Make sense?
 
Thanks, "Big Al". But my basic question remains, "Am I better off to buy a rifle with the SAAMI chamber or the OT&T chamber.

It seems to me the OT&T chamber is more versatile. Here's why... The distance from the base to the start of the shoulder of the SAAMI cartridge is 2.0966". That distance for a 280 Remington is 1.9992". The corresponding distances to the end of the shoulder are 2.1795" and 2.1993". So, it seems to me you could not fire 280 Remington ammo in a SAAMI AI. The case would be too long.

Is that not right?
 
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Avoid the hassle

I've never understood the concept of most of the "improved" cartridges. You usually have to buy or have rechambered a special rifle, get special dies, or hope you can find ammo for them (and pay dearly if you can). All for an extra 100-150 fps which will never be noticed in the field. I have a custom pre-64 M70 chambered for the standard .280, and I get 3,000 fps with 140gr bullets and 2800 with 160 gr. Accuracy is outstanding as well, with some groups around 1/2 moa or less. It's a fantastic rifle chambered for a fantastic cartridge.
 
The so called "improved" cartridges are just a hobby and fun for those that do it the first time.

I fell for it and have a few such rifles.

I am not going to bother with the 280 AI as it seems more snake bit than the others.
 
It seems to me the OT&T chamber is more versatile. Here's why... The distance from the base to the start of the shoulder of the SAAMI cartridge is 2.0966". That distance for a 280 Remington is 1.9992". The corresponding distances to the end of the shoulder are 2.1795"and 2.1993". So, it seems to me you could not fire 280 Remington ammo in a SAAMI AI. The case would be too long.
Click to expand...
In that case you can not fire 280 rem in either chamber that is AI. Both AI cartridges have the same dimension where they headspace which is where the shoulder ends and the neck begins. You would have to use once fired or new empty cases and full length size them with the improved die and load for fire forming. I would get the 280 rem chamber and not mess with it. Then again maybe I would. I fire form 30-30 into 7-30 Waters, that takes the same process.
 
In that case you can not fire 280 rem in either chamber that is AI. Both AI cartridges have the same dimension where they headspace which is where the shoulder ends and the neck begins.
Click to expand...

You could be right but I'm not convinced. I see a variety of numbers for both cartridge dimensions. The only ones we can trust for the SAMMI cartridge must come from SAMMI. For the original, I just don't know (there is no standard).

The only dimensions I've seen for the original give 2.1884" from the base to the start of the neck. That would not allow the 280 Rem at 2.1992" to fit. Maybe the 2.1884 is not correct. Maybe there's enough tolerance that it fits anyway. I've seen multiple posts by original 280 AI owners saying they have no trouble firing 280 Rem's in their guns.

Which is why I'm confused and why I'm now leaning toward going with a 280 Rem and forgetting the AI. Several posters here have suggested that and it seems like good advice.

It's a shame Nosler et al could't have defined the standard consistent with what everyone was using instead of what they and Remington were inclined to use.
 
The whole point of the AI chambers being what it is is that the parent cartridge is a "crush fit". It takes a small amount of effort to close the bolt on the parent cartridge. This ensures zero headspace. The cartridge is fired and the ejected case is an AI.
 
Thanks Brian,

So, in your opinion, should either version of the 280 AI be equally versatile regarding use of 280 Rem ammo and commercially loaded AI ammo (which will surely meet the sammi spec)?
 
Well... I don't know. ;)

Ordinarily, as in the case of every other AI chamber I've seen, the answer would be absolutely YES!

However, the .280AI seems an interesting example.

The difference between most AI and parent dimensions is pretty small. For example, the end of the shoulder is only 0.004" different between the .243AI and the .243Win.

The difference between the OTT .280AI and the parent is 0.109 and the difference between the parent and Nosler AI is 0.0252.

Those both seem a bit more than a traditional crush fit.

I've never known there was an AI that didn't work that way though, so I assume it would be the same. You know what they say about ass-u-me-ing though.:D
 
For what it's worth (if anything) I have Kimber Montana in 280 AI running Nosler brass. I'll say the first pieces of brass I ran through the gun were snug in the chamber, I'm guessing only 1-2 thou interference. Kimber claimed to me that their chambering was in the SAAMI standard, so who knows.

I've not tried fire forming any .280 brass at all, just bit the bullet and got Nosler brass. In my opinion if you're wanting to invest in some "wildcat" then extra costs associated with brass shouldn't scare you off. I understand wanting to fireform, but my times more important to me than that. Not to mention the still volatile component market.
 
I can help you...


There's a little secret about this stuff....

standards are just that... standards. They aren't requirements.

In other words, chamber the thing any way you please. Once the brass is fireformed, it won't matter.

You can headspace a gun any way you please. You'll need dies. Get thee a set of dies, see how they size the brass and set the headspace to 0.002" longer. It'll be perfect.

Viola. Stop stressing.:D
 
In other words, chamber the thing any way you please.
Click to expand...

The problem is, the gun comes chambered from the factory. I am not making this gun. Two different chamberings are available, depending on manufacturer. The question remains, which is preferable?

Go to accurate shooters forum and ask there. Lots of wise long range shooters there.
Click to expand...

Good advice; I did not know about this forum. I'm waiting for a reply there now and will let this thread know the outcome...
 
Can you easily buy brass for both?

Can you easily buy factory ammo for both?

Can you buy dies for both?

If Cooper says that their rifle works fine with both, what's the issue?

I, for my own use, would not buy a Nosler gun in a Nosler cartridge. That sounds like a good way to get left out in the cold.

Buy the old "Tried and True" and don't worry about it.
 
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