I don't know if the .303 is that much better than the 7.62 (.308). I have both calibers and the recoil is just about the same. While recoil is partly a matter of the rifle, it is mostly the round, and full auto with a .303 would be like the M-14 (a weapon that was loved by few, although it still has it's good applications).
The .303 is quite a bit more powerful than the 7.62x39, it is a heavier cartridge and is almost 50% longer than the AK round (3.07" vs. 2.2"). The .303 is very much a full power rifle round, much closer to a 30-06 or 7.7mm than to an AK round.
Maybe Tony Williams would like to offer an opinion. He's the Board expert on small arms.