Yes, the 280 Ross TypeA is a rare item.
I had one which was retailed by George Gibbs and made on a square bridge magnum action.
It was a beautiful rifle but showed high pressure with loads that shot very nicely in another 280 we have which happens to be a Lancaster similar to the rifle in this thread.
The loading info I got from a Ross Seyfreid article but that Gibbs did not like them at all!
I’ll see if I can come up with a photo of the rifle.