Webley MKVI .177 caliber pellet Comparisons of Models

Does anyone know how the 6 inch and 4 inch models of the Webley MKVI .177 caliber pellet revolvers compare in accuracy and range? One reviewer found the 4 inch barrel model to have slightly greater muzzle velocity but less accuracy when compared to the 6. He seemed to know what he was doing and was even a bit more accurate with the short 2 inch barrel than the 4, but admitted that might be simply because it felt better in his hand. One person commented that greater muzzle velocity can cause turbulence at the muzzel that affects a pellet's attempt at straight flight. If so, is that an odd argument for slower projectiles?
 
I have the 6-inch .177 and really need to test it from rest with several different pellets. It feels amazingly like real Webleys I have owned and shot in the past. Everyone who sees and handles it gets a big grin on their face. I did do penetration tests on 1/8-inch wood paneling and had no trouble with full penetration, so I concluded that I could use it effectively and humanely on any rattlesnake that wanders into my yard.