Home Forums Hunting & Shooting Gunsmithing ReChambering Question

My understanding is that the 280 AI is exactly the same as a 280 Remington except for the shoulder.

I also read that to make an AI from a regular 280, the barrel should be set back one thread and then rechambered.

It would seem to me that a 280 AI finish reamer could be used to carefully recut the existing chamber w/o setting the barrel back.

With frequent cleaning, borescoping and headspace checking why would it not work ?

Because it's the wrong way to do it. You'll have excessive headspace with factory ammo to boot.

Yeah, it seems to me that AI cartridges have blown out shoulders which means to me that a reamer would be taking meat out of the chamber - resulting in more chamber space without setting the barrel back. Isn't the 280 Rem hot enough?

Okay, I'll try and show a real gunsmith doing a real test revealed.

Bottom line: there is NO difference in headspace between a 280 Rem, 280 Ackley and 280 AI SAMMI.

This article educated me. I hope it puts another often repeated story to bed.

https://gunsmithtalk.wordpress.com/2012/07/17/280-ackley-improved-emperical-headspace-test/

I would set the barrel back regardless. If for no other reason than to gain a fresh throat while I was at it.

The 280 ai or any other ai done right has slightly shorter head space than the standard cartridge to eliminate any possibility of headspace problems that might be encountered during the fire forming process. That is the main purpose of setting the barrel back.

You are misreading the article. When Nosler registered the 280 AI with SAAMI, SAAMI insisted on go gages that complied with their standards. Previously, folks used a standard 280 Rem gage minus .004". This didn't fly with SAAMI so they redrew their gage. The article is just showing that, contrary to what many think, the old or traditional 280 AI and 280 Nosler AI go gages are the same. They are NOT the same as a 280 Rem gage. If you use a 280 AI gage, old or new, to set headspace on 280 Rem chamber, it will have insufficent headspace.

So, while the "old" and "new" 280 AI go gages are the same, they are not the same as a 280 Rem gage.

Looks like you have retarded figured out, good luck with your [bleep] up [bleep] rifle.

since you are trying to educate yourself on the Ackley cartridge line why don't you go to the source instead of some article from the internet author. get copies of his handbooks and there is an essay on his cartridges and how they were developed. he also goes into the headspace issue with rimless cases and why it is done the way he does it. just saying.

You don't set the barrel back it will end up bitting you in the azz and you will end up doing it anyways, I would set back 2 treads, do it right the first time, and save yourself a headache.

+1 well said, he will learn

Well played sir. Slow learner for sure!

Hmm, not a gunsmith in the bunch I'll wager.

The rifle is NIB so throat is no issue.

I did not misread the link, nor do I find it necessary to be nasty to try and advance my point.

I have every book Ackley ever wrote. The 280 Remington improved is barely mentioned in his 2 volume set.

The gunsmith who wrote the link has proven the original and SAMMI are exactly the same. If you disagree, you have not read it.

It is my rifle that I will load for and easy to fireform cases using the false shoulder method. Don't really care about factory ammo.

If it turns out to be a big issue, the bbl can always be set back.

When it's done, an update will be provided.

Thanks for the advice.

Well, when things go south, we'll be there to tell ya' - "Told you so". In the mean time, I'll keeping a weary eye on the classifieds for anything "280" posted by the OP.

FWIW, I own 4, 280AIs - pre and post-Nosler 'introduction'.

Yep, you have retard figured out quite nicely. Congrats?

While it may work especially if your taking the time to create the false shoulder it is still not the Correct way to chamber an AI. Also your cases will be stretching an awful lot hence the reason most chamber for a crush fit and load touching the lands to fire form.

A utility grade 280 AI I made myself. Chambered properly. It will shoot fireform loads and factory 280 Rem loads into groups almost as small as it will shoot AI loads.



It isn't necessary to setback a barrel a full turn unless the barrel has iron sights. It's only required that you set the barrel back a minimum of .004" (assuming the factory barrel has minimum headspace).

Best of luck, you'll need it.

This AI thing is getting old. To have a true AI it should have a crush fit for fireforming brass. You can move the shoulder anywhere you want and change the angle however you want even change the body taper however you want and you have a 280 Improved not a 280 Ackley Improved, Gibbs improved cartridge had 45 degree shoulders and the the shoulder moved forward quite a bit.

You can use a 223 AI reamer and run it in as deep as you want and use 204 Ruger or 5.6x50 Mag brass, You don't have an Ackley chamber unless it is a crush fit for fireforming. That's the way he designed his chambers.

Can't fix stupid

Maybe my ignorance is showing but is an AI conversion really worth it? As I asked earlier, what's lacking in the 280 Remington? And if lacking, then maybe it's time to move on to another "off the shelf cartridge.