I just recently bought this Mauser 280, more or less just for the heck of it as I still have the dies, brass and some bullets from when I sold my Gibbs magnum.
The numbers all check out.
It has been restocked but to a decent standard of not to original specs. Good feeling rifle though and a good looking piece of wood.

Here’s where it gets interesting.
The stamps all point to being a Mauser retailed rifle rather than an English rifle. No British proofs at all.
Speeds book says that the Mauser 280s were all built on magnum length actions yet this one is on a standard action.
The magazine is made to the correct 280 dimensions which is in fact the longest magazine Mauser offered other than the 416 Rigby and quite tapered from back to front, more so than any other Oberndorf Mauser magazine.

Now, I have a supply of original Kynoch 280 ammunition with 260gr bullets but they won’t fit down the magazine.
They will single load in the chamber as will my reloads.
I was pretty perturbed at this until I read that the original Ross cartridges used a 140gr which seat into the case enough to fit down the mag. This being a pretty early rifle would probably have been built to take these lighter bullets and shorter OAL of that original loading.
It has a long what I would call a heavy sporter profile to the barrel.

Now here’s where I can use some sage advice.
My barrel measures out at a .276” bore.
That makes me think that the projectile should be something smaller than the usual .287” that the Ross is supposed to use.
I think that a .284” bullet as used in the many American 280s may be the right size. I know my Gibbs was tight bored too and had high pressure signs with the same loads that shot just fine in a Charles Lancaster rifle we have.
What do you all think?
Should I try .284s or stick with .287s since they do chamber?

Here are some pictures of the rifle.