I read somewhere that the "Bisley" mods to the Colt SAA were to accomodate the shooting style required at the shooting matches in Bisley, England. I can't find the article, though.
The Bisley-style grip frame has visually more curve and the hammer spur is lower than the standard model. As I recall the article, Colt did that so the gun would point naturally when it was fired with the Bisley-required bent elbow instead of the straight elbow American shooting style.
Can anyone confirm?