Shooting "F" class at the standard 300 meter target, you can do quite well with a rifle which will stay in 2". If shooting on the international target, you'll want somewhat better than that and a rifle which will shoot around 3/8 moa (about 1 1/4 inches at 300M) is necessary to have much chance of shooting a perfect score.
Generally speaking, for most "F" class competition, I'm pretty happy with a 5/8 moa rifle but for the hotly contested 300M international matches, a 5/8 rifle is unlikely to win anything unless everyone else suffers an equioment failure! Regards, Bill.