I have recently purchased a .280 Remington caliber rifle and I'm starting load development for it.
I've handloaded rifle cartridges for about thirty years and prefer to use Lapua brass when possible.
Lapua doesn't offer .280 Remington brass, however they do make 7x64 brass.

SAAMI cartdridge dimensions for 7x64 and .280 Remington seem to be dimensionally so close, that I think one pass through a .280 Rem FL die might get 7x64 brass formed enough to chamber in a .280 Rem chamber.
I also figure brass formed this way would probably also have a bit shorter neck than factory .280 Rem brass - but can't really guess by how much.

I would be very interested to hear from those who have tried this either successfully or unsuccessfully.

the 280 is based off the 30X61 case.
I'd bet LaPua makes 30-06 cases, or 270 win cases which would make things a lot easier.

I didn't have very good luck turning 280 into 7x64. If memory is right, the base is a bit smaller in diameter with 7x64. Your 7x64 to 280 cases may not look so good, but may or may not work OK with full pressure loads. The over expansion may weaken the brass above the web. If you absolutely must use Lapua, as mentioned above, I'm guessing that 30-06 necked down to give a crush fit when fireforming will be the quickest & best option. Cases will be a bit short for a few firings. Using 270 will give proper length cases, but to get proper headspace you will need to expand to 30 then neck back down due to the shoulder being a bit farther forward on the 280 Rem.

Also... Norma used to make good 280 brass but I dont know if they still do.

I'm not sure what continent you're on but Peterson now makes affordable 280 Rem brass & it looks real nice so far. It's next in line when my tired old R-P brass finally wears out (soon I think). I did a velocity comparison test on 5 pieces each of the 4 types of 280 brass I have & the new Peterson seems to have about the same internal capacity as my lot of R-P brass. I used WLR & 47 gr of W760 behind some Remington 150gr SPCL seated to 3.325" firing 5 shot groups on the same day at 85*F. A mild to mid range load with no development, accuracy was minute of deer at 100 yds. with all.

Hornady-2461fps
WW nickle-2486fps
Peterson-2524fps
R-P-2520fps

seems a crime to make 280 brass from 7x64 .. but the base and rim on the 7x64 are nominally .004 smaller ... then again, 12mm caseheads (30-06 sized, or .473) haven't been as large as spec in quite some time...

could it work? yeah .. but as others have said, 270 brass would be a better place to start

I have an old Rem 721 that was rebarreled to 7mm-06 before the 280 came out. My RCBS dies neck down 06’ brass with one pass, no problem. If 06’ brass is usable, I’d go that route. Easy-peasy. Short necks would be a non-issue.

I've shot a 280 Rem for over 50 years. Many times I have had issues finding 280 brass so I have made them from 30-06 brass. Once through the 280 size die with the die backed off enough that there is some resistance when the bolt is closed. Load with a normal charge and the cases form perfectly.