Ported barrel velocity loss?

[Buster95]

Muzzle brakes are mounted at the muzzle of the barrel so no velocity loss but what about ported barrels?

 

[cody c]

Same thing. Holes at the very end of the barrel to manage recoil, essentially the gases will not provide more velocity for the section of the barrel where they will escape around the projectile, essentially the same as shortening the barrel an inch or depending on location of them, but the very slight change in velocity may be negotiable to the benefits of accuracy of lessened recoil, barrel vibration may be stabilized to if its ported like the remington VTR's, and actually I suspect there may be some advantage to not having gases blast out of the barrel around the projectile at the point of it exiting.

Long story short, think of it as shortening the barrel an inch or two.