Is this guy a salesman for oddball stuff?
LOL.
For people who study reloading and ballistics tables, the .280 Remington is perhaps the single best round under .30 cal for hunting and long range work you can put together. Has been for a long time. With modern powders, there’s very little difference between a .280 and a 7mm RemMag now - maybe 150 to 250 fps at the muzzle.
There are more, better bullets available in 7mm/..284 than any other caliber out there now, including .30 caliber rounds.
On my ‘to-do’ list is building yet another Mauser into a .280 Rem.