The answer from lone-gunman theorists began with "maybe Oswald zeroed the rifle at the Sports Drome rifle range." But, whoops, Oswald was known to be elsewhere when Dr. Wood and his son got a up-close, prolonged look at an Oswald double who was firing at that range.
Now, incredibly, lone-gunman theorists' consensus answer is that "well, actually, now that we realize he had no opportunity to zero the rifle, our final answer is that he not only didn't bother to zero the rifle but that he didn't need to zero it anyway!"
Right! Never mind what the FBI's Robert Frazier said about zeroing the rifle with the scope. Yeah, just never mind that. Never mind that the FBI zeroed the rifle with the scope before it was used in the WC's rifle test. Gee, now why did they do that, if zeroing is purely optional and unnecessary?
And never mind that Marine Corps rifle expert Master Sergeant James Zahm told the WC that using the iron sights would have made the shooting feat even more difficult. Just never mind that, too.
To top it all off, they argue that Oswald's alleged shooting feat, even if done with a non-zeroed rifle, would have been relatively easy for anyone with Oswald's demonstrably poor-to-mediocre rifle skills. Uh-huh, never mind that the three Master-rated riflemen in the WC's rifle test--the only test that used the alleged murder rifle itself--utterly failed to duplicate Oswald's supposed performance, even though they fired from only 30 feet up, fired at stationary targets, and were firing with the rifle after it had been zeroed. And never mind that 11 of the 12 riflemen in the 1967 CBS rifle test failed to duplicate Oswald's alleged feat, and that the only rifleman who did scored two hits in three shots in under 6 seconds on his first attempt was an experienced and expert rifleman whose shots were counted as hits even if they landed far outside the small area on the target silhouettes that Oswald allegedly hit.
You see, folks, these guys have a cult-like mentality when it comes to the JFK case. They belong to the small minority of the Western world that still believes in the lone-gunman theory. They embrace the first government investigation, the Warren Commission in 1964, as sacred and definitive, but they reject the second--and far more thorough--government investigation, the House Select Committee on Assassinations in 1977-1979, because that investigation concluded that there was a conspiracy, that there were two gunmen, that a shot was fired from the grassy knoll, that there were at least four shots, that Oswald had suspicious ties with rabid right-wingers and anti-Castro Cubans, that Jack Ruby had significant Mafia ties, that Ruby lied about why he shot Oswald, that Ruby lied about how he got into the police basement to shoot Oswald, that the first hit on JFK was fired when Oswald's view of JFK would have been obstructed by the intervening oak tree, that someone was rearranging boxes in the sixth-floor sniper's nest within 2 minutes after the shooting at a time when Oswald could not have been there, that Silvia and Annie Odio's accounts are credible, etc., etc.
Dealing with these guys is literally like dealing with 9/11 Truthers, Moon-landing deniers, and Holocaust deniers. They're 20 years behind the information curve because they refuse to acknowledge the numerous and historic ARRB disclosures and the scientific research done over the last 20 years that has destroyed the lone-gunman theory.