That's why I said up until 200 yards, loss of velocity in a pistol caliber isn't going to affect accuracy.
A longer barrel allows for more acceleration due to gas pressure to have a longer time to exert more force on the bullet. But all that does is allow a bullet to travel father before lack of velocity starts to hamper accuracy. Unless you are talking very light bullets like a .22s. In those case the shockwave from breaking the sound barrier can catch up to the bullet once it slows down and can throw the bullet into a tumble. Which the tumble would affect accuracy. But that would only be for light caliber rounds fired from very short barrels. Otherwise a .22 is capable of reaching over a mile in distance for trajectory under perfect conditions.