Good afternoon everyone and welcome back to TFB’s Silencer Saturday brought to you by Yankee Hill Machine, manufacturers of the awesome YHM R9 multi-host suppressor. Last week we brought you a look at the Hansohn Brothers Vidar 22 rimfire silencer. Today we take a look at the challenges of adding a beltfed rifle suppressor to a crew served machinegun. Is this the future of beltfed weapon systems? Let’s take a look.
- SILENCER SATURDAY #219: Belt Fed Brutality with the B&T RBS
- TFB Collab: M249 SAW with 1911 Syndicate
- Bow Your Heads – Suppressor Dies Spectacularly to Cyclic M249 SAW
SILENCER SATURDAY#252: Five Challenges for a Beltfed Rifle Suppressor
SILENCER SATURDAY#252: FN M249S – Five Challenges for a Beltfed Rifle Suppressor
‘So there I was..’ is the beginning to a great many alpha, raw meat-eater, hero stories. A battle-worn fighter standing in a sea of steaming hot brass with a thousand-yard stare, modestly realizes that they just saved the free world from destruction. No doubt, some of these STIW stories are true, but rest assured, that is not how my journey with crew-served weapons begins.
Outside of a Weapons Familiarity (FAM) Course and a few demos, I have zero experience with beltfed weapons. But ever since FN America has released a semiautomatic version of the M249 platform, I have been on a mission to own one and run it suppressed. The last leg of the journey is to convert it to a fully automatic post sample machine gun that will be a test bed for “beltfed rated” silencers. I’m still waiting on a few parts to make that possible.
WARNING: The National Firearms Act (NFA) of 1934 and subsequent laws and regulations have heavily regulated firearms like machine guns and silencers. Before you consider modifying any weapon, understand all the rules and the penalties for breaking the law. Personally, I believe the NFA is unconstitutional, but until it is repeated, it is the law of the land.
SILENCER SATURDAY#252: FN M249S – Five Challenges for a Beltfed Rifle Suppressor
The first stop on my suppressing-a-beltfed journey was to better understand how the FN M249 operates and get an idea of how adding a suppressor will change the system as a whole.
The M249 is a gas-operated, belt or magazine-fed, air-cooled, fully automatic weapon that fires from the open-bolt position. The M249 has a maximum rate of fire of 850 rounds per minute. Primarily, ammunition feeds into the weapon from a 200-round ammunition box containing a disintegrating, metallic split-link belt. As an emergency means of feeding, the M249 can use an M16-series rifle or an M4-series carbine magazine, but doing so increases the chances of malfunctions. The gunner can fire the M249 from the shoulder, with a bipod or tripod, or on a machine gun mount. The weapon system has a standardized mounting surface for various optics, pointers, illuminators, and equipment to secure items with common mounting and adjustment hardware. Light Machine Gun, M249 Series, U.S. Army, May 2017
As we have seen in many past Silencer Saturday reviews, semiautomatic firearms that use gas to function the feeding, chambering, extraction, and ejection mechanisms will be effected by adding a suppressor to the system. While gas piston systems, like the one in the M249, have advantages over direct impingement gas systems, restricting or adding more gas will change variables like cyclic rates.
The quick-change barrel is air cooled and has a fixed headspace. The bolt is a multiple lug type which rotates into a positive locked position in the barrel extension prior to firing. Gas is taken from the barrel acting on a piston directly fixed to the bolt carrier (slide). The gas pressure on the old style barrel is based on the gas exhaust system and is controlled by a two-position regulator; one for normal conditions, the other for delivering additional power for adverse conditions. The new style barrel has a preset gas orifice and rotation of the regulator has no effect on its operation. The new barrel has a folding carrying handle, also. The M249 is equipped with a spare barrel in addition to the weapon barrel assembly. The latest barrels have a monoblock design that eliminates the separate gas collar and gas regulator. Light Machine Gun, M249 Series, U.S. Army, May 2017
The earliest version of the M249 included an adjustable gas regulator that allowed the operator to switch between normal and adverse conditions. Adverse conditions usually meant fouling in the action, underperforming ammunition, or other environmental factors that required more gas to operate the action. Later an automatic gas regulator replaced the adjustable gas regulator.
For whatever reason, adding a silencer to the M249 has never been a priority for the U.S. Military. Besides the added cost, weight, and complexity, some argue that the raw sound of strings of sustained automatic fire from a crew-served weapon can have a devastating psychological effect on enemy forces.
On the other hand, there is an increasing focus on protecting our operators from occupational hazards such as toxic gases and particulates and continuous exposures to elevated decibel levels. This is especially true for crew-served weapons where two or three soldiers may be in close range of a single machine gun for extended periods of time. The recent Next Generation Squad Weapon (NGSW) contract and award and the U.S. Marine Corps contract to equip M4s with suppressors is good evidence that the U.S. military is using advanced technology to protect fighters from environmental exposures.
SILENCER SATURDAY#252: FN M249S – Five Challenges for a Beltfed Rifle Suppressor
M249S Para Specifications
- Manufacturer’s Page: https://fnamerica.com/products/rifles/fn-m249s-para/
- MSRP: $10,499
- Users Manual: Click for PDF
- CALIBER: 5.56x45mm
- OPERATION: Closed-bolt
- MAG CAPCITY: 200 Rd. belt or 30 Rd. mag
- WEIGHT: 16 lb.
- BARREL LENGTH: 16.1″
- OVERALL LENGTH: 31.5″ – 37″
- OVERALL HEIGHT: 9.5″
- TRIGGER PULL: 8 – 15.5 lb.
- TWIST RATE: 1:7 RH
Challenges Suppressing the M249/M249S
While it may seem that you can throw on any 5.56mm silencer on the end of a M249 or M249S, there a few considerations that need to be made before you start launching rounds down range.
1. Weight
While this is probably the least of your concerns when suppressing a crew-served weapon, adding another pound or two to an already 25 pound rifle (fully loaded) will start to add up. If you are stuck with a semiautomatic M249S, a lighter weight titanium silencer might make sense if you can pace yourself. Full auto owners probably need to stick with silencers made with steel alloys.
2. Barrel
The M249S Para comes with a 13.7” barrel with a permanently mounted muzzle device to bring the length up to a non-NFA length of 16.1”. You have a choice of buying an 18” barrel and using it as is, cutting to 16.1”, or cutting it down to an NFA regulated length of about 14”. There are also plenty of surplus M249 and M249 Para barrels available from several retailers Don’t forget to get your Form 1 approval before installing a sub 16” barrel.
SILENCER SATURDAY#252: FN M249S – Five Challenges for a Beltfed Rifle Suppressor
I do not recommend attempting to remove the permanently installed muzzle device that come on the included barrel. The weld almost covers the full circumference of the barrel.
3. Muzzle Threads / Mounting
If you decide to buy a surplus Para barrel, the thread pitch is a non-standard 9/16x24LH which will limit your mount choices. I found an original KAC M249 Para mount for the KAC NT4 5.56mm suppressor on GunBroker (please don’t ask how much I paid). Rugged makes a dedicated mount for the short barrel M249. And there is a muzzle adapter from 9/16x24LH to 1/2×28 from XCaliber Silencers/The Silencer Store. But tolerance stacking is always a concern and the barrel/mount shoulder doesn’t seem to be an exact match. More testing is needed before we try out other suppressors.
SILENCER SATURDAY#252: FN M249S – Five Challenges for a Beltfed Rifle Suppressor
4. Gas System
Back pressure is an issue when suppressing gas operated guns and the M249/M249S is no different. Some of the toughest and quietest suppressors ever made are also the ones that can cause the most back pressure into the rifle’s action. Since there is no factory made adjustable gas regulator, you may want to use a flow-through style suppressor that doesn’t add any extra pressure to the system. We’ll talk about a few options in future Silencer Saturday episodes.
5. Rates of Fire
5. Even in a semiautomatic configuration, 200 or even 300 round strings of fire will punish and possibly damage the heartiest of silencers. As with magazine fed rifles, letting the barrel and silencer cool every 30 to 60 rounds will prolong the life of the blast baffle. Of course, since the barrel swap on the M249 takes less than 10 seconds, you could always have a few silencers mounted up on barrels ready to go. Zombie preppers rejoice.
Coming Soon
I shot my first strings of fire today with the KAC NT4 and it does sound great. We will be testing a few different 5.56mm suppressors on the M249S and a few more once the full auto version is complete. Then we will venture into some more specialized setups that I am really excited to test out. See below.
SILENCER SATURDAY#252: FN M249S – Five Challenges for a Beltfed Rifle Suppressor
Thank you to FN America, Ballistics Research & Machine, and all the ammo companies who keep cranking out 5.55mm rounds. I’ve been buying as much as I can afford to prepare for these tests.
Thanks for reading. Be safe, have fun, and we’ll see you back here next weekend for another Silencer Saturday.
Silencer Saturday is Sponsored by Yankee Hill Machine
