You're thinking about a rimmed cartridge. The rules for the .22 are for a rimfire cartridge where the primer solution is internally poured into the space inside the rim. The rules for the centerfire ammo is ball ammunition only. Nothing in this contest can be Match Ammunition.
I know the difference between rimless, rimmed, and rimfire but I thought the .303 was a rimfire.
I'm too cheap to buy match grade stuff anyway but when I start reloading maybe I'll fiddle with making some.