this makes for good reading
New and Improved: The .280 Ackley Improved - RifleShooter
The .280 Ackley
New and Improved: The .280 Ackley Improved - RifleShooter
The .280 Ackley
Now to muddy the water in the below article click on the case and you see the case that was in Sierra manual and Nosler before Nosler decide to do the SAAMI Spec 280AI. On page two of the article they mention loading data from those manuals.
.280 Ackley Improved | Gear | Guns & Ammo
That case in those two manual is what Nosler changed for their SAAMI spec 280AI. My new Nosler 280AI brass length is 2.525"
Interesting and the base to neck/shoulder junction reads 2.175 which is only .001 off the above diagram of the supposedly new saami version. Tis only a sketch though.