I was checking SGAmmo to see if they had any 303 Brit in stock, they did not but they did have other milsurp calibers in stock.
6.5x55
7mm Mauser
8mm Mauser
7.62x54R
http://sgammo.com/catalog/rifle-ammunition
6.5x55
7mm Mauser
8mm Mauser
7.62x54R
http://sgammo.com/catalog/rifle-ammunition