Barrel length & fps?

[Bullet]

I have a Glock 22 and am thinking about purchasing a Bar-Sto barrel. The barrels come in 4 lengths (4.5 – 5 – 5.5 – 6 inches). What difference in bullet speed (fps) would the different length barrels make shooting Speer 180gr Gold Dots?

 

[PO2Hammer]

Very little with modern autopistol ammo. Maybe 50 fps from a 4.5" to a 6 incher.
The difference from 3" to 4.5" is far more significant.