I don't know about Elvis, but Oswald was a lousy shot.
Colonel Allison Folsom, who examined Oswald’s Marine Corps records for the Warren Commission, testified that Oswald’s record showed that his marksmanship was “not good” and that his average score over a two-day period was 36 when “people should get a score of between 48 and 50.”
In addition to his testimony, Colonel Folsom sent a letter to the Warren Commission on June 8, 1964, regarding Oswald’s marksmanship. It states that a Marine would qualify as an Expert with a minimum score of 220, would qualify as a Sharpshooter with a minimum score of 210, and would qualify as a Marksman with a minimum score of 190.
Folsom stated that according to Oswald’s Marine Corps record, on May 6, 1959, four months before his defection to the Soviet Union, his score was 191, one point above the bare minimum to qualify as a Marksman.
Folsom also stated, “A low Marksman qualification indicates a rather poor shot and a Sharpshooter qualification indicates a fairly good shot.”
Colonel Folsom’s information clearly shows that two and a half years after Oswald’s first two months of intensive Marine Corps training, he was one point above the bare minimum to qualify as a Marksman, Oswald was nowhere near a “fairly good shot.” He was most definitely a “rather poor shot,” even though he was still firing at a stationary target with a Marine-issued M-1 rifle on a Marine Corps rifle range.
Let's look at that 191 sharpshooter score. The Marine Corps rifle qualification involved firing 50 rounds into targets at ranges from 200 to 500 yards. A single round scores anywhere from 0 points (missed the target entirely) to 5 points (hit the center). Anyone scoring a 191 would hit the target a minimum of 191/5 times, rounding up. That is, they would hit the target a minimum 39 or 50 times or 78% of the time. Even a "poor shot" in this test would be a far better marksman than some would think.