Love the .303 and the weapon that surrounds it, but the .308 (7.62mm) is a brilliant military round. It has looked after us for half a century and remains the round of choice for machine guns, despite many attempts to find something better.
The versatility is fantastic: our snipers use a heavy bullet variant for the L96A1 sniper rifle to take it out to the 800-1000m range envelope; in the last few years, however, the .338 Lapua Magnum has 'nipped at the heels' of 7.62mm and the Army broke into its 'piggy bank' to buy every sniper a new AI .338 Super Magnum - which they were quite pleased about! The SM, derived from AW, is a great jump forward from the PM Infantry sniper rifle (L96A1).
I like the 7.62mm, but I love the .338. Sneakily though, the EOD guys in Iraq have convinced someone to buy them the .50 AW40. I saw some .338 armed snipers looking a little bit 'green with envy' at the EOD guys with their .50s.
I understand now that the SEALs are buying the AI semi-auto .50 AS50 - which must upset Barrett quite a bit. I suppose that healthy competition will generate better weapons in the future.