"That so called 600 yard shot has been talked about for thirty years or more, and I don't believe it. "
I do.
Elmer did it earlier but he wrote and I read about it in his column in Guns and Ammo in the latter half of the 1960s, including giving the names of those who had been there when he did it. Of course a lot of gun rag writers immediatly poo-pooed the story (perhaps especially the very pompous expert on all things, Col. Askins, USA, Ret.) and they misrepresented it as something Elmer was boasting about or promoting. The truth was - as it so often is - much different.
The deer in question had been moderately wounded by a hunting client, it ran but stopped at that range. Elmer only had his S&W 29 revolver with him so he used it because he had no confidence he could shoot the client's rifle with sufficent precision. He was almost as surprised as the others when it dropped and they paced off the distance.
The whole point of his story was to prove that the lethal effect of his big semi-wadcutter could do the job a long way out if the target could be hit. He was obviously correct and hitting game at long ranges with big handguns using iron sights was Elmer's specialty.