A further point is that you are very unlikely to get .308 on a first FAC for field use. 7.62 x 51 is purely a military calibre, the civilian version being known as .308", the diameter of the bullet. It is regarded as suitable for large deer, red and sika, and wild boar. Previous posters gave said most of the rest, and I would just add that for field use your best bet is .22lr. With your CCF training you would be welcome as a member at most .22 target clubs as well.
You might well get .308 for target use but have to keep gun and ammo at the club where you shoot.
ATB,
Ric