Hi! What are most accurate cartridges for that range? Don't really care about "stopping power" just pure accuracy. How tight can be the groups at that distance, what's the best wind dodger and flat shooting cartridg and most important for novice easy to learn to use?
Best Regards
As others have said, the quality of the barrel and action usually trumps the choice of cartridge. But to get good at long range shooting requires much more than a good rifle, it requires range time and lots of it. The more shooting you can do at long range, the shorter the learning curve becomes. The less expensive the shooting is, the more of it you can do in any time period. Thus all things being equal, a .223 can be as accurate at 600 yards as a .338 Lapua, but while the .338 doesn't take as many clicks of elevation to get a 600 yard zero or as many clicks to correct for wind at long range, you could send 5 rounds of .223 down range for the cost of each round of .338.
During the early stages of your training, MOA groups should be your goal. There will be days when that goal is illusive, but sticking to it will pay off in the end. Begin at closer ranges, and when you can shoot a MOA group on demand, under good conditions, extend your range. On the days when you can't seem to make hits, shorten the range and attempt to determine what went wrong.
Concentrate on the basics of marksmanship. Work out how to properly grip your rifle, assume a repeatable cheek weld with the proper eye relief, check your parallex, and assume a relaxed position. Learn to acquire and check your natural point of aim. Develop a surprise break on the trigger, a surprise break should not startle you, just surprise you at the moment it happens. You should be able to place a coin on the top of the barrel near the muzzle and dry fire the rifle without knocking the coin off the barrel; start with a quarter and work towards using a dime. This requires real concentration and follow through to master, so don't expect to get it on the first try. Dry firing is a very useful tool in that it allows you to see where the bullet would have hit had you made a real shot, where the sights point when the striker falls is where the bullet would have gone. Learn to breath for each shot and hold it at your natural respiratory pause and follow break the shot in that narrow window before you must breath again. If you gasp for breath after breaking the shot, you waited too long to shoot. If you hold the sight on the target too long before firing, the target image will burn into your subconscious and you will not notice minor errors in your sighting. Learn to fire as quickly as conditions allow. If you are not shooting in a genre that imposes a time limit, impose one on yourself.