Open (iron) sights waver around even if your gun is well supported, and tripods can be restrictive. Way to be accurate is knowing exactly when to fire - I mean your gun sight will be wavering, so over distance that waver is badly accentuated. You learn to be accurate mostly by grouping shots: fire where you think you will hit, say 5 shots, then check the target to see where you hit. Important also to keep your shot process
consistent: sight on target - make sure you view the sights exactly the same every time, also notice your trigger pull.
Not every gun sight is accurate, so usually try the 5 shots first. Then even if your gun is sighted, it may give a bad spread. I had a cheap shit semi-auto with a bad spread, bullets all over the place, but fun to shoot
Aiming rl is a similiar process in KF with no sights that Nc3 was telling a guy who complained about no sights. You get used to it. Also in KF or any 1st per shooter, you learn about 'lead fire' - shoot slightly ahead of a moving target.
Trouble with guns is ppl soon get bored with paper targets