Fume extractor. Holes in the barrel allow propellant fumes to exit and diffuse from there. Beats the heck out of propellant fumes in the crew compartment upon opening the breech to reload.
“Fume extractor. Holes in the barrel allow propellant fumes to exit and diffuse from there. Beats the heck out of propellant fumes in the crew compartment upon opening the breech to reload.”
I believe that they also help to reduce the recoil