Unclebob...
And after all, in a sense you also had a point.
With 'regular' ballistics it is usually the case that the longer the barrel, the further and more accurate a shot will be.
The reason for this is that as long as the projectile is in the barrel, there will be propellant (the expanding gas created by the charge going off) behind it, pushing with a force greater than the friction the projectile has with the barrel, resulting in constant accelaration as long as the projectile is in the barrel (although it is theoretically possible to create a barrel so long that the propellant will no longer push, as the gas has reached it's maximum volume, after which the projectile's velocity will decrease. Let's call this the maximum effective length).
For this reason the barrels on tank guns are usually so long; they are meant to speed up their projectiles to a tremendous velocity, because it is the momentum of the projectile that causes it to pierce it's target's armour. Many tank guns have a calibre of 50 or more, meaning that the length of the barrel is 50 times as long as it's internal diameter, or bore. The Leopard 2A6 has a 120mm gun with a calibre of 60, meaning it has a length of 7,20 meters. That's one BIG gun.
the reason that the maximum effective length of a barrel in paintball is far lower is because the propellant used to launch the ball is 'bled off' far quicker. This is because paintball barrels have portings (most of the time), as well as a breach that is not fully sealed. True, the bolt closes off the breach, but it also retracts really quickly, allowing a lot of propellant to bleed off that way. (obviously Cockers and the like work a little different, perhaps this explains their great efficiancy) A tank gun has a breach that is totally sealed off, meaning no propellant is lost when a shot is fired.
Besides, the gases we use have a far lower pressure than the stuff used to fire real bullets.
Hope this cleared things up a little.
And don't stop posting.