Barrel length effects velocity, and a longer sight radius allows for easier aiming. I've only seen one documented experiment with barrel length, and it was done with a 44 Remington Magnum. A group was shot out of a Ransom Rest, after which one inch was cut off the barrel, and the barrel re-crowned. It was a Ruger Super Blackhawk that started with a 10 1/2" and ended with an 1 1/2". Group size never changed, it just kept getting lower on the target as velocity fell off.