Just got a rebarrel back from my smith. Its a model 70 classic with a douglass barrel in 280 ackly improved. He had the barrel sitting there chamberd & threaded for the classic, and the dies and all so I said what the hell screw it onto my old 06 and lets see if I like playing with the AI-thing.
I have 50 new brass ready to fire form, but I got some alreay formed brass with the rifle, too.
also 4 loaded rounds. All feed and chamber fine but realizing its probly not the exact headspace as the rifle he took the barrel off,
I was thinking a smart way to go woud be to fire form a few of my new cases and measure them and compare to the already formed ones, and If they are real close to the same I should be all right. Or mabye just load one of the preformed with a light charge and measure before and after fireing. Am I on the right track or should I toss the preformed brass and start over ? what do you think am I playing with a dangerous head spce thing here, ...tj3006

Take the already formed AI cases, full-length resize them in your dies, and then fire them with a medium load in your new rifle.

They'll be fine.

If you want to be extra safe, fire a factory 280 round in the Improved chamber, and compare it to the formed brass you were given. Eyeball comparison is fine.

Garrett

You mean it is possible that your gunsmith stuck a barrel onto your action without checking the headspace? Doesn't sound like a good career move too me.

The headspace on the Ackley Improved chamber should be set so that you feel a slight amount of resistance when closing the bolt on a factory case. This is done to hold the case firmly in place, at the neck/shoulder junction while fireforming your brass.

Easy fix if your concerned, just take the brass and neck it up to .30 cal and then progressively neck it back down to .280 until your just able to close the bolt on a case. In my experience, headspace with the AI cartridges is the personal choice of the reamer grinder and I don't think there is any real "standard" on them. The neck-up and backdown method precludes any headspacing problems.

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Originally posted by Masterifleman:
Easy fix if your concerned, just take the brass and neck it up to .30 cal and then progressively neck it back down to .280 until your just able to close the bolt on a case. In my experience, headspace with the AI cartridges is the personal choice of the reamer grinder and I don't think there is any real "standard" on them. The neck-up and backdown method precludes any headspacing problems.

Seems like an awful lot of work for something that you should simply be able to throw a round in and fire. Headspace is set by the gunsmith, not the reamer grinder. There IS a standard. Ackley set it when he designed his line of improved cartridges based on rimless cases, and today that is the guidlines most gunsmiths follow when setting the headspace for the Ackley Improved chambers.

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I don't think there is any real "standard" on them

There is a AI standard. Problem is some gunsmiths don't bother to do it correctly. Many not bothering to set the factory barrel back a turn before they rechamber.

I think this barrel was never chamberd for the standard 280. Its a douglas 23 inch and has a model 70 featherweight countour.
I fireformed 6 rounds today and it went fine. the only thing I did not expect was that the case mouth opend quite a bit.
Then I ran them up into my size die and although I do not like the neck tennsion.
They brought it down well enough. I will probably make some adjustments and figure out how to do this a little better. Its my 1st improved round...tj3006

As you work more with it, remember that you need full-house loads to fireform. Sometimes people new to the AI rounds back off of the fireform loads to save powder and you will begin to experience a lot of split shoulders if you go too low. By too low, I mean similar to starting loads in the manuals.