I think you will be interested in reading "The Ultimate In rifle Accuracy" By Glenn Newick.
The people shooting these kind of groups are using slow twist 6mm cartridges with light bullets, at very high velocity, in bolt guns. Its called Bench Rest Shooting, and they compete at 100 or 200 yards, so its short range though very precise, and many of the techniques they use can be used in hunting or other types of competition.
Some of these techniques I've adopted are Case Neck turning, Primer pocket uniforming, Flash Hole deburing, Sorting Cases by weight as well as by head stamp, and neck sizing or partial full length sizing where action type permits it, not auto loaders of course, or pumps and lever actions.
The proper mating of the scope to the action, and the action to the stock, is what I personally see as the most common mistake among those friends I shoot with and I've been guilty of this myself in the past, but that is how you learn too, if you have a real interest in the shooting sport and you don't have to shoot competitive to learn to shoot precision long range, though it might help. I've never had the time or money for that, but I now have a battery of very well tuned rifles, though none of them are very expensive, and ammo for them.
Keep it fun!