0331 Machine Gunner
When a rifle company needs to suppress a fixed enemy position, sweep a wood line, or anchor a defensive line with sustained direct fire, the machine gun team answers that need. The 0331 Machine Gunner is the infantry Marine who owns that weapon system, understands how it fits into the larger fight, and keeps the guns running through everything the field throws at them. This is still infantry first, but with heavier steel and a different set of technical demands.
Job Role and Responsibilities
The 0331 Machine Gunner is responsible for the tactical employment of light, medium, and heavy machine guns and their support vehicles in direct support of rifle squads, platoons, and companies. These Marines provide sustained direct fire to suppress enemy positions, support infantry maneuver, and maintain weapons-system readiness through all phases of combat operations.
Daily Tasks
Machine gunner daily life is divided between weapons maintenance, tactical drills, and field training. The gun system demands constant attention to remain reliable. On a typical day, tasks include:
- Field-stripping, cleaning, and function-checking the M240B, M2 .50-caliber, and Mk 19 grenade launcher
- Range qualification and crew drills including immediate action, emplacement, and displacement
- Squad and platoon-level field exercises with fire team integration
- Vehicle maintenance for assigned support vehicles used to move heavy guns
- Physical conditioning and weapons carry work
Specific Roles
| Classification | Code | Description |
|---|---|---|
| PMOS | 0331 | Machine Gunner |
| NMOS | 0365 | Infantry Squad Leader |
| NMOS | 0369 | Infantry Unit Leader |
| AMOS | Advanced machine gun qualifications earned through the Advanced Machinegun Course |
Mission Contribution
Machine guns extend the range and lethality of a rifle platoon beyond what individual riflemen can achieve alone. During an assault, the gun team pins the enemy while riflemen maneuver. During defense, machine guns anchor fire lanes and force the enemy to funnel into channels where they can be destroyed. Without machine gunners, the infantry’s ability to maintain fire superiority in a sustained engagement is significantly reduced.
Technology and Equipment
Primary weapons include the M240B 7.62mm medium machine gun, M2 .50-caliber heavy machine gun, and Mk 19 40mm grenade launcher. The M249 Squad Automatic Weapon is part of the weapons platoon picture in certain configurations. Machine gunners also operate HMMWV variants used to move crew-served weapons. Day and night optics, bipods, tripods, and traversing-and-elevating mechanisms are all part of the crew’s technical load.
Salary and Benefits
Financial Benefits
Pay follows the 2026 DFAS active-duty enlisted pay tables, effective January 1, 2026.
| Rank | Grade | Under 2 Years | Over 2 Years | Over 4 Years |
|---|---|---|---|---|
| Private | E-1 | $2,407.20 | $2,407.20 | $2,407.20 |
| Private First Class | E-2 | $2,697.90 | $2,697.90 | $2,697.90 |
| Lance Corporal | E-3 | $2,836.80 | $3,015.00 | $3,198.00 |
| Corporal | E-4 | $3,142.20 | $3,303.00 | $3,658.50 |
| Sergeant | E-5 | $3,342.90 | $3,598.20 | $3,946.80 |
Source: dfas.mil, 2026 Enlisted Basic Pay Table.
Additional Benefits
BAS of $476.95 per month applies to all enlisted Marines. BAH varies by duty station and dependency status. TRICARE Prime covers all active-duty medical, dental, and vision needs at no cost. The Post-9/11 GI Bill covers full in-state tuition at public schools and up to $29,920.95 annually at private schools (AY 2025-2026 cap).
Work-Life Balance
Machine gun units operate at standard infantry tempo, which means field exercises, deployments, and irregular hours are the norm. The weapons maintenance requirement adds time beyond what a rifle platoon typically needs, particularly before and after field events.
Qualifications and Eligibility
Basic Qualifications
| Requirement | Standard |
|---|---|
| Citizenship | U.S. citizen or lawful permanent resident |
| Age | 17-29 for initial enlistment |
| Education | High school diploma or GED |
| AFQT minimum | 31 |
| ASVAB line scores | EL 90 or GT 90 or MM 90 minimum |
| Water survival | WS-B required |
| Physical | Infantry initial strength and combat-arms MOS classification standards |
| Medical | Meet MEPS medical standards |
The triple-composite option (EL, GT, or MM at 90) reflects the combined mechanical and technical demands of maintaining and employing crew-served weapons. Marines who score strongly in any of those three areas meet the published threshold.
Application Process
Enlistment begins with recruiter contact, ASVAB or PiCAT testing, MEPS physical, and contract negotiation including infantry field selection. After Boot Camp, Marines attend ITB and then the Machine Gunner Course at SOI East or SOI West. The MOS is formally awarded upon completion of the Machine Gunner Course.
Selection Criteria and Competitiveness
0331 is a specialist slot within the infantry field. It is more competitive than a standard rifle assignment because fewer seats exist and the line-score requirement filters out the lower end of the infantry accession population. Strong test scores, clean records, and high physical performance all help.
Upon Accession
Marines enter at E-1. Standard active-duty enlistment is four years. Bonus availability tied to infantry or weapons specialties should be confirmed with a recruiter.
- ASVAB Online Course Guided lessons and timed practice for the line score this MOS needs.
- ASVAB Study Guide Self-paced study with full-length practice exams and answer explanations.
Work Environment
Setting and Schedule
Machine gunners work in weapons platoons within infantry battalions and weapons companies. The work environment is field-oriented, with range time, outdoor exercises, and vehicle operations making up the bulk of non-administrative days. Garrison periods include maintenance schedules and planning cycles.
Leadership and Communication
Team and section leadership runs from Gun Team Leader (Corporal) to Section Leader (Sergeant). Communication during field operations is radio, hand-signal, and voice at the crew level. Performance feedback is immediate given the visibility of each Marine’s contribution to the section.
Team Dynamics and Autonomy
The gun team is one of the tightest small-unit structures in the infantry. Ammo bearer, assistant gunner, and gunner roles are interdependent. Individual reliability is essential because the gun cannot function effectively with a weak link in the crew. Junior Marines are expected to master their position before advancing to the next.
Job Satisfaction and Retention
Marines who take pride in weapons mastery, enjoy field training, and value the technical identity of the machine gun community tend to stay. The MOS has a distinct culture within the infantry. Those who expected general infantry work and find the weapons-specific demands burdensome sometimes transition after their first enlistment.
Training and Skill Development
Initial Training
| Phase | Location | Duration | Focus |
|---|---|---|---|
| Boot Camp | MCRD San Diego or Parris Island | 13 weeks | Marine Corps fundamentals, basic combat skills |
| Infantry Training Battalion (ITB) - Infantry Marine Course | SOI-West (Camp Pendleton) or SOI-East (Camp Lejeune) | 59 days | Fire and maneuver, offensive and defensive operations, patrolling |
| Machine Gunner Course | SOI-East or SOI-West | Varies | M240B, M2, Mk 19 employment, crew drills, direct-fire fundamentals |
Advanced Training
- Advanced Machinegun Course for team and squad leaders
- Infantry Small Unit Leaders Course for squad and section leaders
- Combined Arms Staff Officers Course for senior NCO development
- Joint exercises and unit-level gunnery evaluations
Career Progression and Advancement
Career Path
| Rank | Grade | Typical Time in Grade | Primary Responsibility |
|---|---|---|---|
| Private | E-1 | 0-6 months | Schoolhouse |
| Private First Class | E-2 | 6-12 months | Ammo bearer, learning crew |
| Lance Corporal | E-3 | 12-18 months | Crew member, assistant gunner |
| Corporal | E-4 | 18-36 months | Gunner, gun team leader |
| Sergeant | E-5 | 36-60 months | Gun section leader |
| Staff Sergeant | E-6 | 6-10 years | Platoon sergeant, weapons platoon |
| Gunnery Sergeant | E-7 | 10-16 years | Company gunnery sergeant |
Role Flexibility and Transfers
LATMOVE from 0331 to other MOSs is available with command endorsement and available school seats. Machine gunners commonly pursue moves into law enforcement, intelligence, or reconnaissance. The combined arms expertise also translates well into instructor billets.
Performance Evaluation
Proficiency and conduct marks govern Lance Corporals and Corporals. FITREPs govern Staff Sergeants and above. Advancement in a weapons platoon is closely tied to demonstrated technical mastery, section leadership performance, and physical standards.
Physical Demands and Medical Evaluations
Physical Requirements
Carrying and emplacing the M240B (27 lbs) plus a combat load across terrain is physically demanding. Heavy machine gun mounts and ammunition cans add significant weight to field movements. Machine gunners carry more than the average rifleman. Sustained fire operations require physical endurance even when seated or in a supported position.
| Test | Event | Male 17-20 Minimum | Male 17-20 First Class | Female 17-20 Minimum | Female 17-20 First Class |
|---|---|---|---|---|---|
| PFT | Pull-ups | 3 | 23 | 1 | 7 |
| PFT | Crunches (2 min) | 70 | 100 | 70 | 100 |
| PFT | 3-Mile Run | 28:00 | 18:00 | 33:00 | 21:00 |
| CFT | Movement to Contact | 3:38 | 2:55 | 4:40 | 3:48 |
| CFT | Ammunition Lift | 42 | 95 | 42 | 95 |
| CFT | Maneuver Under Fire | 3:37 | 2:27 | 4:20 | 3:15 |
Source: marines.com. Verify current year standards against official Marine Corps publications.
Medical Evaluations
Standard MEPS screening applies at accession. Hearing checks are conducted more frequently for machine gunners given sustained exposure to large-caliber weapons noise. Annual physicals and dental exams are required throughout the career.
Deployment and Duty Stations
Deployment Details
Machine gunners deploy with infantry battalions and MEU Battalion Landing Teams at standard infantry tempo: typically one seven-month deployment every 24-36 months. The weapons platoon deploys as an integral part of the rifle battalion. Machine gun sections have participated in operations across the Indo-Pacific, Middle East, and Europe.
Location Flexibility
Primary duty stations for machine gun units are Camp Pendleton, Camp Lejeune, Kaneohe Bay, and Okinawa. Twentynine Palms hosts combined-arms exercises and some weapons-battalion elements. Assignment preferences are submitted but not guaranteed.
Risk, Safety, and Legal Considerations
Job Hazards
Sustained weapons fire creates significant noise and heat exposure risk. Carrying heavy systems increases musculoskeletal injury probability. Direct combat risk in deployed environments is high, consistent with all infantry roles.
Safety Protocols
Range safety standards, crew-served weapons handling procedures, and field safety SOPs govern all live-fire events. Crew training includes immediate-action drills for stoppages, cook-off prevention, and safe handling of misfires.
Security and Legal Requirements
0331 does not require a security clearance at the PMOS level. Billets in higher headquarters may require one. All Marines are subject to UCMJ and applicable Rules of Engagement in deployed settings.
Impact on Family and Personal Life
Family Considerations
Infantry deployment cycles and field-exercise tempo create real family impact. MCFTB, Military OneSource, and MCCS programs support families at all major installations. Machine gun unit families at Camp Pendleton and Camp Lejeune have access to full support networks.
Relocation and Flexibility
Two to three PCS moves during an initial enlistment are typical. Machine gun units are concentrated in major infantry-battalion locations. Geographic preferences should be discussed with a recruiter before signing a contract.
Marine Corps Reserve
Component Availability
Reserve infantry units carry weapons platoon structure, and 0331 billets exist in the reserve component. Availability depends on unit type and location.
Drill Schedule and Training Commitment
Standard reserve commitment is one drill weekend per month and two weeks of Annual Training per year. Weapons reserve units typically schedule additional range and gunnery events to maintain proficiency on crew-served systems.
Part-Time Pay
A reserve Corporal (E-4) earns approximately $419 per drill weekend based on 2026 pay rates. Active-duty monthly pay of $3,142.20 for the same grade is significantly higher.
Benefits Differences
| Benefit | Active Duty | Marine Corps Reserve |
|---|---|---|
| Monthly pay (E-4) | $3,142.20 | ~$419 per drill weekend |
| Healthcare | TRICARE Prime, no cost | TRICARE Reserve Select (premiums apply) |
| Tuition Assistance | Up to $4,500/year | Available on qualifying orders |
| GI Bill | Full Post-9/11 GI Bill | Montgomery GI Bill - Selected Reserve |
| Retirement | 20-year pension at 40% of high-36 | Points-based, collect at age 60 |
| Deployment tempo | Higher, structured cycles | Lower, mobilization possible |
Deployment and Mobilization
Reserve machine gunners can be mobilized under Title 10 orders for contingency operations and overseas deployments. Typical mobilization length is six to twelve months.
Civilian Career Integration
Weapons accountability, maintenance management, and infantry leadership experience pairs well with law enforcement, security, and first-responder careers. USERRA protections apply to reserve service.
Post-Service Opportunities
Transition to Civilian Life
The Transition Readiness Program provides career counseling, resume preparation, and job-placement support. Federal Veterans’ Preference applies. The Skillbridge program allows terminal-phase active-duty Marines to intern with civilian employers in the final 180 days of service.
Civilian Career Prospects
| Civilian Job Title | Median Annual Salary | Job Outlook (BLS) |
|---|---|---|
| Police and Sheriff’s Patrol Officer | $70,900 | +3% |
| Security Guard / Security Manager | $38,400 - $63,000 | +3% |
| Firefighter | $56,560 | +4% |
| Armorer / Weapons Technician (Federal) | $62,000 | Stable |
| Emergency Management Specialist | $79,180 | +5% |
Source: Bureau of Labor Statistics Occupational Outlook Handbook.
Is This a Good Job for You? The Right (and Wrong) Fit
Ideal Candidate Profile
The best 0331 candidates want to master a heavy weapon system, enjoy field work with a tight small-unit team, and have the mechanical aptitude to keep equipment running under field conditions. Marines who like technical challenge within a physical infantry environment, and who take satisfaction in being the unit’s most reliable direct-fire capability, find this MOS rewarding.
Potential Challenges
Marines who dislike carrying heavy equipment, performing repetitive maintenance, or working in weapons-specific team structures may find 0331 less satisfying than a standard rifle platoon. The physical load is higher than a rifle assignment, and the technical maintenance requirement never goes away.
Career and Lifestyle Alignment
The MOS builds leadership, weapons expertise, and team accountability under stress. Benefits including the GI Bill and tuition assistance provide the path to civilian credentials that complement that experience. Law enforcement, security management, and federal employment are the most direct civilian parallels.
This site is not affiliated with the U.S. Marine Corps or any government agency. Verify all information with official Marine Corps sources before making enlistment or career decisions.
More Information
Contact your nearest Marine Corps Recruiting Station to confirm current 0331 school seat availability, contract options, and any current bonus programs tied to infantry weapons specialties.
Explore more 03 Infantry roles, including 0311 Rifleman and 0341 Mortarman.
Need score context? Review the ASVAB guide and the PiCAT guide before publishing permanent MOS content.