I just wanted to post a quick statement as many people like to debate this topic. Yet it is not a long enough topic to make a whole post on. Mini Topics will be short, sweet, and NOT posted on the forums so if you want to read and comment on them you will have to come here!
Longer Barrels shoot further, period. I know we have all seen videos and read opinions of people who would beg to disagree but all of these tests lack one thing, scientific logic. Now I can go and shoot a 10 inch barrel and compare it to a 14 inch barrel and say they shoot roughly the same distance. Of course I could also look at two water bottles one filled with water and the other with ethanol and they look roughly the same. Here is where things get a little tricky according to the laws of physics with the same parameters if two objects of similar mass leave a point at the same speed and height they will travel the same distance. So if you were to move one of those objects four inches further ahead of object number one and have them keep the same speed and height the object that was moved will travel four inches further. Now, will it take a greater force to propel the paintball, yes but it will shoot at least four inches further.