I've cast and reloaded for .303, 8mm Mauser and 8x56R (for my M95 Mannlicher rifle and carbine). I used the Lee 185gr mould for .303 and sized the 205gr 8x56R bullets to .323 for use in my Mausers. All my bullets were gas checked.
I initially used the Lee Manual, and relied heavily upon the C.E. Harris article at Cast Boolits about loads for military surplus rifles. I also relied upon some articles at surplusrifle.com, in particular the one about producing #2 Alloy with wheelweights. If you are willing to pay attention to all of the little details that go into bullet casting, I think you'll find it rewarding, even if your first batch of cast might be a bit frustrating. I've done a couple of batches of bullets, and by the second or third batch was both producing decent bullets and getting good results, having figured out what worked best in my different rifles. Looking back, I probably would have remelted the bulk of the bullets that I used in my first batch of ammo, since even after repeated remelting and casting, it took a while to produce bullets without minor blemishes.
I was looking at Lee's .309 150gr mould for possible use in a Swiss K31, some .308 Mausers, maybe an M305 and Garand. I'd use the faster loads in the autoloaders to make them cycle and maybe load some lighter loadsfor plinking purposes with the boltguns. IMR Trail Boss is apparently a good powder for producing generic, low cost, low power loads, so reloading with that powder looks like my upcoming winter project.
You might have to research a bit deeper to find a good load for the .300 Win Mag, since it has such a large case capacity, but myriads of loads for .30/30 and .308 are available to suit your particular needs.
Good Luck,
Frank