A new policy was put in place some time ago ago.In a Marine Corps rifle platoon, the platoon sergeant also carries a pistol. Any attached crew served weapons, such as machine guns & mortars will have some personnel carrying a pistol and not a rifle. Pistols are used in combat more than you think. My experience anyway.
PISTOLS IN THE PAST WERE ASSIGNED TO ALL MARINE OFFICERS,
SNCOS, AND NAVY BILLETS. THE NEW ASSIGNMENT POLICY ASSIGNS PISTOLS
TO MARINE COLONELS AND ABOVE, NAVY OFFICERS, AND NAVY
E6 AND ABOVE ONLY.
THE M4 CARBINE WAS PREVIOUSLY ASSIGNED ONLY TO SPECIFIC UNITS.
THE NEW ASSIGNMENT POLICY ASSIGNS THE CARBINE TO MARINE LT THROUGH
LTCOL, WO/CWO, SNCOS, NAVY E5 AND BELOW, AND LIMITED EQUIPMENT
VEHICLE OPERATORS.
THE M9 PISTOL QUANTITIES HAVE BEEN REDUCED SIGNIFICANTLY WITHIN
THE OPERATING FORCES.