Depending on the powder and load there is a point of diminished return with a barrel which is too long. The powder being fully burnt before the end of the barrel can actually slow a bullet down. On the other hand I had someone reloading for me and I noticed unburnt powder being expelled (nice fireball). So ... If the right powder and bullet combination is used ... Longer will give a higher velocity, but ........
depends on the purpose I suppose. this could be a pocket carry for someone tremendously tall and skinny, and with an incredibly deep pocket ... or maybe not skinny ... maybe this is Shaq's CCW gun 😆🤣🤣