I gotta admit----I'm puzzled---(this doesn't take much)---I was unaware that Winchester ever chambered a rifle in .280 Rem. I also went to the "Blue Book" and left puzzled again, but learned that indeed, the 280 was offered in a '70 featherweight from '81-'94, and a Classic Featherweight in '92. If it was offered in anything else at any other time, I missed it.
Maybe this will help pin it down a little better. Good luck.