M240B Machine Gun: Machine Gunner Review

What’s my favorite gun of all time? I mean ALL TIME!

Not my favorite from my collection and not my favorite I can purchase at any gun store. I mean, my real favorite gun.

It’s the M240B.

For five years, I served as a United States Marine Machine gunner, and I loved my job.

I got my hands on guns like the M16A4, the M4, a Mossberg 590A1, an M9, and of course the M249 SAW, the M240B, the M2, and MK19.

Shooting a belt-fed machine gun is something everyone should experience at least once. It’s so much fun.

I deployed with the M240B twice and carried it as a gunner in a machine gun team. Not to mention, I also used it to instruct non-machine gunners and foreign military forces.

It’s gone with me on top of mountains in Africa, stormed beaches, and crossed the Helmand River.

We became close friends. While you can’t go down to your friendly gun store and grab one of these things, they are neat pieces of machinery.

So, I figured, why not break this gun down and talk about its cool features and look at its role as the main weapon of a machine gunner in a line company.

Ready to learn more? Well, keep reading.

Breaking Down the M240B

FN Herstal built the original FN MAG machine gun.

When the United States military wanted to replace the M60, they settled on the M240. Without a doubt, the M240 is superior in nearly every way.

The M240 operates on a long-stroke gas piston system, operating on an open bolt system.

Officially, the M240 serves as a gas-operated, belt-fed, open bolt, air-cooled, crew-served, fixed headspace general-purpose machine gun.

General Purpose Machine Gun, or GPMG, is a concept to have one machine gun to serve many roles.

As such, the M240 is found in the hands of foot-based infantry, on trucks, on guard posts, on helicopters, on tanks, APCs, AAVs, boats, and more.

The M240B model was built upon the Gulf model and implemented a hydraulic buffer system to help reduce recoil. It also offered a Picatinny rail system and a simplified gas system.

M240B rails are often adorned with laser aiming devices like PEQ15s.

The gun comes with an integral bipod — easily connected to the classic M122 tripod. In training, Marines use the tripod extensively, but in combat, it never left our FOB.

Belts of ammunition feed from the left, and gunners load the belt with the cover closed or opened.

Loading with the cover closed allows the machine gun team to quietly load the gun and protects any optics from a hot barrel.

M240B Barrel & Belts

Speaking of barrels, the M240B’s quick-change barrel ensures gunners don’t burn the barrel down.

All a runner needs to do is hit the barrel release, pop the handle up with a karate chop, and remove the barrel – replacing it with a new, cooler barrel takes even less time and is done with ease.

Capacity varies depending on just how many belts you want to link together.

When I patrolled, I carried a 50-round belt loaded into a cloth sack that we crudely called a nutsack.

Fifty rounds acted as a “starter belt” so the gunner could lay down suppressing fire immediately.

Belts can be connected to ensure the gun never actually runs out of ammunition, and a good team can keep an M24B running for nearly forever.

The M240B qualifies as a crew-served weapon, and by doctrine, the gun has three crew members.

One serves as gunner, one as ammo man, and another as team leader who is also an A-Gunner.

Team leaders help load the gun, change the barrel, control the rate of fire, and pass orders from the squad leader.

The ammo man provides rear security and brings ammo as necessary while the gunner fires the weapon (obviously).

While that’s the most fun job in the team, it also necessitates the gunner carrying the gun regularly.

At the Range and In Combat

At the range, the M240B offers only full-automatic fire.

A simple cross-bolt safety takes the gun from safe to full-auto, with a cyclic rate of 550 to 650 rounds per minute.

It’s quite controllable, and an experienced gunner can fire controlled bursts to land accurate fire on target.

Controlling the weapon on both bipods and tripods does take some training and experience, though.

Marines advise right, tight, and down when using a tripod.

With a bipod, you grab the stock with your non-dominant hand and shove it into your shoulder as you fire.

Anything fully automatic takes some practice to control. Without proper control, the M240B will beat you up and toss you around.

You’ll open up your beaten zone so much; the gun becomes much less effective.

Accuracy

When Marines exercise proper recoil mitigation and control, the M240B proves extremely accurate.

With a tripod and a good firing position, the M240B can hit targets out to 1,800-meters. My squad and I have done just that with an old burned-up car being our target.

The sound of a burst striking metal carries quite far and makes it easy to know when you’ve made contact.

Cars are big targets, but to be fair, it was over a mile away, and I was using iron sights.

My team leader used binoculars to walk me onto the target. Once we were on target, we laid down hate and discontent.

Lots of our ranges offered a multitude of reactive targets that fell when hit.

We had zero issues hitting these man-sized targets at 300- to 500-yards with just a few bursts.

Not to brag, but on one range, my team was so efficient with hitting targets our maneuvering rifleman had nothing to shoot.

The peep sights are surprisingly fine and function well to get the gunner on target.

Admittedly once on target, you can break your sight picture. Within 600-yards, the tracers from the 7.62 belts can get you on target without the need for sights.

An optics rail over the top allows for the use of day and night optics.

The Marine Corps adopted a Trijicon Machine Gun Day optic, but I hated it.

It felt like 3-pounds of waste on a gun that doesn’t need an optic to do its job, but maybe I’m just a Luddite.

Control and practice make the M240B an extremely accurate weapon, even as the weapon heats up.

When things get too hot, we swap barrels and give the first one time to cool. In fact, I would say this takes more skill to shoot accurately than any other weapon I’ve handled.

Ergonomics

Ergonomics are all over the place. But as a machine gun, it’s not exactly made to be ergonomic.

What it excels at is reliably laying down fire.

Loading from the left makes it easy for the A-Gunner to keep the weapon loaded and firing.

Pop the top, and the A-Gunner can drop a new belt in place.

A solo gunner can reload the weapon, but it’s a slower process because of the 50-inch length of the weapon. The shooter must move around the weapon to do so.

The right side charging handle requires the shooter’s hand to leave the firing position.

You can’t do the Haley under the gun charge with this thing.

Links and casings eject out the bottom of the gun and create a nice little pile beneath the gun, preventing the casing from being flung into the gunner and A-Gunner.

The bipods lock in place under the handguard easily enough and look massive.

Their large size allows them to lock into place and pop in and out.

It’s rapid to drop and get into a hasty bipod prone and start laying down fire as necessary.

Let’s be real…everything on the M240 looks and feels massive.

The charging handle, safety, stock, and top cover are huge and easy to activate and use.

That big stock provides solid lockup into your shoulder and makes balancing out the recoil easier.

I’m always suspicious when I see rifle stocks on machine guns. Like, how comfortable is a stock designed for a 5.56 rifle going to work on a 7.62 machine gun?

Ergonomics are strong….except for the 27.1-pound total weight of the gun.

A spare barrel weighs another 6.6-pounds. In short, it’s a hefty gun. After carrying for miles every day on foot, I had killer legs.

It’s also a gun full of corners, sharp edges, ridges, bolts, and all sorts of stuff that pokes and prods as you carry it.

There is no way to carry it for long periods completely comfortably.

Every machine gunner finds his way of doing it, though. I relied a lot on a two-point sling, carting it around more like a rifle.

As a 49.7-inch weapon, maneuvering in vehicles, buildings, and even alleys was never fun.

This gun will never be used to clear rooms. Well, until we train gorillas to use them, of course.

Reliability

My M240B never failed me. In literally tens of thousands of government-sponsored rounds, the gun always went bang.

I’ve fired so much ammo through one in such a short time; I lit my cigarette off the barrel…while it was raining.

It needs just a little lube every now and then, but it will keep going.

The M240B’s long-stroke gas piston system doesn’t need much love to keep running either.

At a training event in UAE, a sand storm set in on us. This sandstorm disabled nearly every other weapon, but the M240Bs still fired without remorse.

I’ve used one in the humid hills of Spain, sand-ridden mountains of Djibouti, and frigid temperatures of Romania without complaint.

They work full of dirt, mud, and sand without argument.

By the Numbers

Ergonomics: 4/5

It’s so dang heavy! Other than that, the weapon’s layout makes it easy to use, load, and fire. It’s not fun to carry, but boy, oh boy, it’s fun to shoot. The big controls work well with gloves and make it easy to keep the gun running.

Reliability: 5/5

A little CLP helps ensure the gun runs, but I’ve never seen it fail — even when forced to feed blanks in austere environments and tasked with eating hundreds of rounds in a short period.

Accuracy: 4/5

It’s only a step down from a sniper rifle when mounted to a tripod. By itself, the gun can be tough to control enough to shoot accurately without plenty of experience. However, with a max effective range of 1,800 meters, it’s tough to beat.

Looks: 2/5

It’s a pig, an ugly pig. It doesn’t have much going in the looks department, but you can see its World War II heritage.

Overall: 5/5

Do I have a bias for the M240B? Yep. A big one.

Conclusion

I love this gun without shame and find it the most reliable machine gun in the USMC’s arsenal. It works better than the SAW, the M2, and the MK19, providing platoon-level firepower in a man-portable package.

I love the M240B, and I loved being a machine gunner. There is a deep satisfaction you get when you’re carrying the biggest gun in the gunfight.

It’s an outstanding piece of machinery, and I don’t see it going anywhere anytime soon.

Any other gunners in the group? Let us know what you think about the M240B in the comments below. Or check out my machine gunner’s analysis of the new FN Herstal Evolys.