High quality modern day double rifles mostly have gas venting hollow screws. Generally they go unnoticed because they are covered up by engraving. As an example, here a pic of the action of my FN-Browning CCS25 in 9,3x74R showing the (engraved) gas screws :

Looking closely, you will pick up the slot and silhouette of one engraved screw in the scalop at upper chamber's mid-height. The lower bbl. screw sits in the middel of the action (engraved acorn), in line with the 1st.