The 0306 Infantry Weapons Officer, commonly referred to as a Marine Gunner (Gunner for short), is the eminent warrant officer MOS in the Marine Corps. The Marine Gunner is a Chief Warrant Officer specifically trained in the employment and training of infantry battalion organic weapons, gear and assigned personnel and in the basics of Combat Marksmanship.

Gunners are Special Staff Officers employed as the principal advisor to commanders at all levels. They assist in the development of training and employment plans designed to ensure Mission Essential Task compliance. They help design and vet the weaponeering and training policies of the commander and help to disseminate information to the unit's personnel regarding such policies. They generate and quantify reports on the unit's technical and tactical weaponeering proficiency and brief the unit commander as to where each subordinate unit sits in regards to his intent.

Gunners also mentor the officers and Marines of the unit in all applicable mechanical, doctrinal and conceptual weaponeering and training matters as required to improve the general effectiveness and proficiency of the command. They have oversight of the unit's ammunition allocation and annual weapons requalification and certification programs. They accommodate all weapons organic to the MAGTF.

They perform additional duties such as Battalion Landing Team (BLT) Gunner ISO of a MEU, Team New Equipment Training (NET), new weapons systems and gear research and development, foreign weapons training, participation in applicable Course Curriculum Review Boards (CCRB), new curriculum development for marksmanship and infantry related tasks, vetting of draft Infantry and Marine Corps Common Skills Training and Readiness Manuals and fire support planning.