The FN IAR is based on the SCAR. It has a rate of fire of 650 RPM and weights in at 10.4 lbs.

Picture 4-20
FN IAR. Click to expand.

One very interesting features is that it switches automatically from closed bolt to open bolt depending on the chamber temperature. From FNH-USA:

Today FN offers the new Infantry Automatic Rifle (IAR), a unique, highly-adaptable, modular selective fire weapon system that fills the roles of both individual battle rifle and squad automatic weapon in one light, compact package. The magazine-fed FN IAR is capable of firing from a closed bolt in both semi-automatic and fully-automatic modes, yet automatically transitions into open-bolt operation in semi-automatic or fully-automatic before reaching cook-off temperature for a chambered cartridge.

I do not think the temperature switch would be electronic. Most likely there is a piece of metal that expands when heated and causes a switch from closed to open bolt.

Again, a bit thanks to Daniel Watters for pointing this out to me.

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • gummywormz

    so are they going to give it a 100rd drum magazine?

    • gummywormz, yes, it is one of the IAR requirements.

  • jdun1911

    Are you sure about that? There are a lot of problems that associate with them, historically. New gears have to be develop to hold the drums. I would hate to be the guy carrying three or four.

    I think in the end the Marines will go with 40 or 45 magazines.

  • Sean Nack

    this seems like a bad idea to me, but i just can’t put my finger on why. i think it’s the drums; the 100 rnd “nutsacks” are much smaller and easier to carry than the drums. i’ll be the first person to say that the SAW should probably be replaced, but i don’t think that the problem is the linked ammunition; that concept works fine in the 240 and the M2, although i was never a big fan of the Mk19. i mean, i wasn’t an armorer or a SAW gunner, i couldn’t tell you what the exact problem was, but it always seemed like it had ridiculously close tolerances for even a light machine gun, and it was undoubtedly a pain to disassemble, even harder than it’s big brother the 240. so if close tolerances are the issue, it seems like you’re just making that worse by relying on that capability in an assault-rifle-sized weapon. i just have this vision of a gunner walking around with these HUGE “mag” pouches hanging off of him…a lot of dudes just rolled the 200-rd drums which i imagine are, i believe, similar in size to the 100-rd circular drums, while the 100-rnd sacks are about, oh, 3 inches tall by 5 or so wide? it’s been two years since i’ve handled or seen one, keep in mind. but it seems like you’re getting half the ammo for double the weight/bulk, which is not a good deal in my mind. this just smacks of, in 20 years, somebody saying “it seemed like a good idea at the time.”

    • This is just my guess, and I have no military experience so take it for what it is worth, but I reckon the automatic rifleman will be carrying one, maybe two, 100 round magazine and a bunch of 30 round magazines. I think this is the case because those 100 round drums are not reliable. If one of those jams the rifleman will lose a significant percentage of the ammo he is carrying.

      Has anyone used the Russian RPK ( http://en.wikipedia.org/wiki/RPK ) or one of the semi-automatic clones. How does it compare with the SAW.

  • jdun1911

    The IAR is the RPK/BAR. That’s what the Marine wants, a true light machinegun that can keep up with the team. The SAW weight around 21 pounds. A fully loaded BAR is lighter then an unloaded SAW.

    The Soviet got rid of their drums. The RPK-74 use box magazine, no drum.

    Drum are unreliable and not durable enough for the battlefield. 100 rounds drum is over 3 times heavier then a 30 round magazine. The spring has to push three time weight at a speed that can keep up with the rifle cycle. That’s is very hard to do consistently. When a full loaded drum drop to the ground it can/will be damage. Any damage to the drum will effect reliability (Thomson’s drums are notorious for this).

    I am surprise the Marine want drum magazine. Countless hours and money has been thrown at it over 100 years to make it work.

    40 or 45 rounds magazine are the way to go IMO. They’ve proven to work.

  • Stretch

    “The fancier the plumbing the easier it is to clog up.” – Montgomery Scott
    Looks like FN is trying to out-complicate HK. Just re-chamber the BAR or BREN to .223 (shudder) and be done with it.

  • Sean Nack

    i’m pretty sure the SAW is 15 lbs unloaded, i don’t know about the BAR, but in either case i concur with the spirit of jdun’s statement; the magazine/drum isn’t a good idea. our SAW gunners rolled two 200 rounders (still in the drum, usually), and usually a couple of 150’s, so about 700 rnds (if i remember correctly; again, not a SAW gunner, so i might be a little off) and maybe another drum in the pack on a foot patrol. so if you figure that the 100-rd mag/drums are about the size of the 200 rd drums, those take up a pretty decent chunk of the FLC…you could maybe put a couple of normal mag pouches up on top of the vest, but you couldn’t do a full UBL (7 mags), and 200 rnd drums on one vest, at least you couldn’t do it without pulling off other things like NOD’s, canteens, and the like. you might be able to squeeze another couple of 200-rnd mag pouches on top, i seem to remember some people doing that initially, although i don’t think it lasted very long. i think i’m pretty firmly on the linked-ammunition side of things, which i guess makes me pro-drum and anti-magazine (the difference, as i understand, is that the drum is for linked ammo and the magazine is spring-loaded?) although i’m sure there’s a more efficient way to handle linked ammunition, both on the side of the links themselves and the internal mechanism. i’m mystified by all this; it just doesn’t seem practical.

  • R.A.W.

    This comes from a deep part of the errornet rumor mill, but a reasonably reliable one so take cum grano salis

    The open bolt/closed bolt cutoff switch in the FN IAR is not electronic. It’s functions by a little tab of metal (either a thermocouple or a shape-memory-effect alloy) that changes shape as the chamber heats up and flips the switch. Sort of like the mercury vial in a thermostat.



  • DSvet91

    The cause of the SAW reliability problems are caused by operator error. The the feed system of the M249 is far to delicate with lots of stamped metal bits that are easy to tweek out of alignment. It just takes one laps of concentration in the heat of battle to turn a very effective problem solver into 14lbs of useless. It make me cringe every time I think of Gomer Pile looking confused while he tries to load a new belt in his shiny new toy with the bolt forward… clunk… clunk… “Why won’t this thing close?” clunk… clunk… “Maybe if I slam it really hard.” CLUNK… CLUNK…

    As for the magazine vs. linked ammo debate, why not both? How about a modular weapon system that can be configured as magazine only, belt only, or both magazines and belts. There is only one real option for a M249 companion/replacement, the Shrike Modular Weapon System. Light weight, dependable, field configurable and all mounted on the familiar M16/M4 lower receiver. What more could you want? Add the open bolt/closed bolt fire controls of the LWRC IAR or the FN IAR and you would have the perfect IAR contender. But why stop there? With the Shrike’s belt feed capability, it could replace the M249 entirely. And with no stamped metal bits to tweek, it may even be Gomer friendly.

  • spencer

    this just doesnt seem like the most bang for the buck. especially FN’s scar variant, quick change barrel? ha, 6 torque screws that need a specially pre loaded torque tool? oh and if you think spec war actually likes the thing or chose it ask your nearest seal, alot of politics kept the chosen 416 out of their hands anywhoo atleast colt put on a quick change barrel. it all seems like fore runners for whats to replace the m4, the scar, 416 or another colt, but if this is truely a supressive fire weapon these seem to be horrible choices, i like the concept of the ares shrike, same familiar m4 platform but either belt fed or magazine fed, and if its true the saw is a big target the shrike is cosmetically identical to the next guys m4 so spend some money making it soldier proof and bam, good to go.

  • Brad


    Ditto on the RPK question. The first thing that popped into my mind upon hearing of the USMC IAR project, was that the RPK is exactly the sort of weapon the fills the IAR role.

    As far as box vs drum feed, the Chinese and Singapore seemed to have been happy using drum fed squad automatic weapons, unlike the Russian RPK experience. I understand the Chinese made drum for the RPK is somewhat different and much easier to load and unload than the Russian design.

    I have also heard rumors that the Russians experience from fighting in Grozny influenced them to prefer 7.62×39 caliber weapons to those in 5.45mm. Supposedly the 5.45mm was inferior for shooting through walls, floors, ceilings and other typical urban cover. That sort of area fire would seem to directly reflect on caliber selection for a squad automatic.

    (Maybe it’s a good thing for the new Iraqi army that 7.62×39 RPK remains the squad automatic weapon?)

    I appreciate the problem the USMC is trying to solve with the IAR. The USMC fire-team needs an automatic weapon suitable for suppression and the assault roles, given the limited quantity of people in a fire-team. The M-249 is too clumsy for use in assault.

  • Ryan

    I don’t see the need for a magazine fed SAW. The role of the SAW is to lay down suppressive fire, lower capacity mags mean more mag changes. The more mag changes, the less time the weapon is firing. It might take a little longer to put a new belt in a 249 (I hate the 249) but at least there will be 200 rounds there when your done.

    You don’t need a fancy thermostat (that WILL break) to switch from closed bolt to open. What’s the need of a SAW to fire from the closed bolt anyway? Its not meant to be a precision weapon, It just needs to put down suppressive fire. If the barrel heats up you can just change it on a 249.

    I think this is a waste of time and money for nothing. Why did we stop using the BAR in the first place? Fire Power!! I think we are better served with linked ammunition.

  • Destroyer

    Ryan, the intention of the IAR is NOT TO REPLACE THE SAW! it is to increase the firepower of infantry squads and fire teams by complimenting the SAW and carbines/rifles. Adding the IAR concept to infantry units would do wonders in terms of firepower and flexibility.

  • Travis

    Why is it that responses to just about every article I read about the M27 always include suggestions to bring back the Browning Automatic Rifle? Didn’t that thing have a habit of BURSTING INTO FLAMES on the guy using it? I realize the M27 is pretty much a 21st century equivalent to it, but still.

  • charles222

    Bursting into flames wasn’t just a BAR issue…it was a problem for the M1 as well; apparently hot barrels contacting wood isn’t such a hot idea. :p

  • SamsMyName

    I see how this could compliment the SAW. Especially if there are say 4-5 of these with larger capacity mags. Doesnt some companies make a 40 or 50 round magazine for the M16/M4?? I have also seen a dual drum mag for the AR line of rifles thats supposed to take a lot of punishment and keep ticking. I dont know for sure if its really good or not though

  • Redchrome

    I am kind of failing to see the reason for an automatic switch from open-bolt to closed-bolt operation. What’s wrong with firing semi-auto closed-bolt, and full-auto open-bolt? I can kind of forsee cook-off problems with lots of semi-auto fire; or going full-auto for a while and then back to semi-auto; but introducing a doodad that’s bound to be fragile seems like a solution in search of a problem.

    Sean Nack,
    a ‘drum’ is a magazine with a circular or spiral feed of cartridges and no belt. I think what you’re thinking of are ‘belt boxes’, which hold belted rounds in a box (which may be round). The Germans call theirs belt holders for the MG42/MG3 ‘sturmtrommeln’ or ‘assault drums’; and the RPD circular belt boxes are usually called ‘drums; but this is really just a confusing special case usage… generally speaking, a ‘drum’ means it doesn’t use a belt.

    I don’t have any experience being shot at; but I do think that having the *option* of giant-capacity magazines is a good one. Jerry Miculek points out that 100-round Betaco mags actually stick out the bottom less than 30-round magazines, so you can get down into a lower prone position with them. Jim Sullivan has said that they timed a man on the move trying to load a new belt into an M249 and it was over 20 seconds; whereas a mag change takes only a few seconds (even if it’s a giant mag). So there’s a lot to be said for magazines of various sizes, to suit your tools for the task at hand.

    I have no idea what happened to the Shrike. Rumor has it that there’s a trickle of them coming out. It seems like a pretty good idea and I’d love to get ahold of one; but I also wonder why other companies haven’t picked up the basic idea… I suspect there’s non-obvious flaws. (price possibly being one of them, durability likely to be another). If the concept could be perfected tho (which may require a whole new platform — keep in mind that the Stoner 63 wasn’t adopted in large numbers either) it may be the best of all worlds, offering belt and magazine feed (of whatever magazine size you can make work with an AR15) with no parts change.

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