Originally Posted by Pistolgripshotty
The longer the barrel the more velocity...its simple physics.
Simple physics that turns out to not be true.
The powder eventually stops creating more pressure than the bullet/barrel friction.
Some cartridges (typical handguns) this number can be as low as 12-15 inches. 22 rifles might be around 16-18 inches. Many small capacity rifle cartridges might stop gaining speed around 22-24 inches.
No reason shotguns would be different. Longer does not always mean faster.