Ain't that the truth...be prepared for a sore shoulder.
You know what people do sometimes?
Knock the components (powder charge and bullet) out of cheap corrosive 7.62x39 ammo.
Reload them straight into new or once used .303 brass. (yes, using the elastic band trick to fireform)
Gives you the cheapest possible ammo, lighter than normal .303. Just the ticket for a JC.
edit- I see others have recommended 7.62x54 ammo. Same idea. The Combloc ammo is the best deal around these days.
BTW, I was told a trick about getting the bullets out. First, push them in a bit, to break the seal of the lacquer. Otherwise they can be hard to pull. (using a kinetic bullet puller)