at 300m theres a lot more factors to take into account other than just the caliber,the quality and consistancy of the ammo for one.300m isnt really a long way any well build well loaded caliber should be able to hold an inch or less,
With my stalking outfit I'd be very pleased with a 1" group at 300m using 5 shots of factory ammo. If I picked up a heavy barrelled target rifle with high mag scope etc (as I sometimes do at bisley) and put 5 hand loads into a 1/2 inch group at 300 I'd be v pleased too!
Realistically though I've rarely seen anyone shoot that consistently (do it a few times in a row) - there are always flyers, gusts of wind, and screw ups that people just seem to discount!
If you're consistently in 2" at 300m I think you're doing very well!... We can't all be Olympic quality shots
Calibre wise I don't think any have the edge, though more is known about the 308 than most other calibres
Every r93 ive owned has done sub 1" at 300y 3 shot, thats 22-250, .243, 2 x 25-06 and a .308. My 6.5x47 sako 75 built by redmist shot 3.75" 5 shot at diggle, that was 500y in a wind changing from 0 to 8 mph.
Depends on how much time you have and what sort of position you can get. When stalking only the first round from a cold barrel counts. So once happy with zero, grouping serves no purpose as the barrel will be warm.
amazing that the 308 is very seldom used in target shooting nowerday and even sporting shooting.times move on mate even though the 308 was one of the most popular hunting and target caliber.the 7mms have taken over the realy long range stuff as the little 6mms have blizts the sub 300 yards comps
each to there own i suspose