USMC used to qualify at 500 yards (460 m). We used a 20” wide by 40” tall silhouette target for the M-16. I could put 7 out of 10 rounds in it from the prone position, slow fire.
Before the M-26, with the 7.62 M-14 we used a 20” diameter round bulls eye. 7 out of 10 also.
Iron sights?