<XMP><BODY></xmp>Support fire version of the M16

        USMC have recently being trialling candidates for a weapon they call the IAR (Infantry Automatic Rifle). A lot of BS has already been written about this weapon replacing the M249 SAW, but according to Patrick Cantwell, capability integration officer for the Infantry Automatic Rifle program at SysCom:-

        “The plan is to buy 4,100 IARs and reduce the number of SAWs in the Corps from 10,000 to 8,000, Cantwell said.
        “We are still going to maintain SAWs in the company,” he said. “Only 2,000 SAWs will be replaced. The reminder will be kept as an organizational weapon for when commanders need them.”
Marine Corps Times

        An interesting feature of this weapon is they have 16” barrels, making them much handier weapons than a SAW or M16 for operations such as house-clearing. With a 16” barrel the IAR will also have a higher muzzle velocity and better ballistics than either a 14.5” M4 or 13¾” barrelled Para M249.
        The design selected seems to be the HK416 candidate. The quoted weight of 7.9lbs seems dubious since this is effectively the same weight as given for the standard HK416 rifle.
        I'm not sure this is the best choice since the other candidates also seem to have features worth incorporating. The LWRC candidate fires from a closed bolt for semi-automatic fire and an open bolt for automatic fire. The FN candidate isn't based on the AR15/M16/M4 series but automatically switches from closed bolt to open bolt operation when the breech becomes hot enough. The Colt candidates (right) combine a heavy barrel with a heat sink mechanism. Defence Review suggests that an equal if not superior weapon could be made from M4s in service with off the shelf add-ons.
        A common feature to all models is the Grip Pod, a clever device that combines a vertical foregrip with a retractable bipod.

Support Fire Version of the M16

        Recently I've been trying to think of ways to improve logistics. Some of my thoughts can be found at

Tracked Trucks and Tactical Pallets.
Very Heavy Lift Helicopters for Vertical Replenisment
Escort and Patrol Companies for Convoy Security
Better Protected Trucks
        In particular I was thinking of the composition of the dismounted element in the Escort and Patrol units. When they dismount the troops would need to move fast, but have considerable firepower. I felt that a ratio of weapons like that of the dismounted force of a Bradley platoon would be best- one third of the men carrying M249 SAWs and one third M16s with M203s. E & P platoon dismount elements would actually be larger than those of Bradley platoons.

        Problem was, a CSS unit was not likely to get that high an allocation of SAWs. This brought me back again to an old idea, a heavy barreled support version of the M16.
        Here I'll caution against "Either/Or" mentality -the automatic assumption that when the adoption of one thing a new piece of equipment is suggested it means the scrapping of another piece.

        I'll stress here that I'm not suggesting that the M249 Minimi be replaced. The H-bar M16 is an additional weapon.

        In many secondary vehicles the only armament is two or three M16s. Wouldn't it be nice to know that a third of these had LMG capability? This would be particularly welcome given that standard M16A2s are semi-automatic and tri-burst only. H-bar M16s will probably prove popular with units that must carry a lot of other gear such as LRRPs.

        The M16 H-Bar will be several pounds lighter than a M249 so fitting accessories such as night sights is less of a burden. The weapon might also mount the M203 if this was desired.
        LMG versions of Assault rifles, sometimes called Machine Rifles have been used by many armies, probably the best known being the RPK. Many armies have also used the FAL-HB alongside their FALs (SLRs) and MAGs (GPMGs).
        Heavy and Fluted barrels for the AR15 have been available for a long time and several nations already use the M16 in an LMG role. Heavy Barreled versions of the M16 are in use by Canada, Brazil, El Salvador, the Dutch Marine Corps and the US DEA. The USMC experimented with M16-LMGs. Their version probably had the ugliest fore-end ever placed on an Armalite.

Canadian AR-15 LMG
Another Canadian AR-15 LMG
Colt LMG
Diemaco LSW
Diemaco LSW (PDF)

        A very basic H-bar M16 can be created just by adding a bipod and heavy barrel and changing the selector mechanism. Other refinements can be added, which include:-

        Ciener make a belt feed conversion for M16/AR15 weapons. Weapons such as the Ultimax and RPK have proven effective in the SAW role without needing belt feed so M16 H-bars will probably use MWG 90 round drums or 100 round “C-mags”. Both are commercially available and the latter will fit in a standard ammo pouch and will probably prove popular with riflemen too. Conventional box mags clipped together may also be used.

        Weight is a topic that usually comes up when comparing belt and drum fed weapons. For a given number of rounds having them on a belt is usually lighter than using a magazine/drum. This page gives the weight of a loaded metal US-issue 30rd box magazine as 1.01 lbs and of a 200rd plastic box for a M249 as 6.92 lbs. (Lighter and Heavier versions of the M16 magazine do exist, the weight given is for the standard issue variety). Jane's Infantry Weapons 1976 gives the weight of 100rds of linked 5.56mm without a carrying container as 3lb. Jane's Infantry Weapons 2003 states that the 150rd and 200rd loaded belt carriers for the Israeli Negev MG as being 5.94 lb and 7.48 lb respectively. The same source gives the loaded weight of the 100rd drum of the Ultimax 100 as 4.18 lbs. The MWG 90rd is 3.6 lb loaded and three 30rd magazines clipped together weigh around 3.3lb. The C-mag is described as 1kg unloaded which suggests a loaded weight of 4.8 lb.
         While belt feed is lighter than magazines the gulf between them is not that great, at least for the number of rounds likely to be carried by an infantryman. Depending on carrying system using belt instead of drum or box magazine saves about 10%, but this does not take into account the weight of the weapon. Possibly not all of the ammo load will be carried in magazines/drums. It may be practical to carry a proportion as lighter stripper clips that can be used to reload the magazines. To our reckoning we must also consider the difference in weight between the different weapons. The drum feed Ultimax weighs only 9-10.1 lbs compared to the 15-16.75 lbs of the belt-feed M249. Another important consideration is that new drums can be loaded into a weapon more rapidly than any belt and that many designs of drums can also be used by accompanying rifleman. This Ultimax article points out that the Ultimax can be reloaded while the gunner is on the move, something very difficult for a M249 gunner to do. Many armies, such as those using the RPK seem to have no major problems with using drum-feed weapons at squad level.

         Another common concern about drums is that of reliability. This seems to vary between different designs. The drum mag of the Thompson was not noted for its reliability and this may be the source of such concerns. On the other hand the drum of the Suomi and PPSh-41 were noted for being very reliable.

MWG 90 rounder website.
"Military Morons" opinion of C-mags and Chinese Drums
Chinese 120rd Drum mag for AR-15
AR-15 magazines FAQ including Drums.
The Suomi drum. Famous for its reliability.

        Most rifles fire from a closed bolt for increased accuracy, while weapons such as machine guns and SMGs usually fire from an open bolt to aid cooling. Some weapons, including the Johnson LMG I believe fired from an open bolt for automatic fire and a closed bolt for semi-automatic. Most Heavy Barreled versions of Assault rifles are modified to fire from an open-bolt.
         Theoretically an open-bolt weapon is less accurate than one that fires from a closed bolt. In practice this may not be an issue, at least for when a weapon is being fired from a bipod and a well braced firing posture. Ralph Zumbro recalls how the M1918 BAR could hit a 12” target at 300yds and place all 40 rounds from two magazines in a two foot area at 500yds. The BAR fired from an open-bolt. The L86 also fires from an open-bolt and has apparently demonstrated a capability for accurate long range fire.

         The Beretta Model 70-78 (left) was a Light Support version of the AR-70. It was not placed in production but did have an interesting and simple barrel change mechanism. A barrel latch on the top of the weapon was lifted and the barrel pushed forward with the fore-end to disengage from the receiver and gas cylinder. The bipod was mounted on the gas tube over the barrel rather than on the barrel. The foresight of each barrel was adjustable to so differences in each barrel can be compensated for when zeroing.

        ARES Defense systems produces a replacement M16 upper that converts the weapon to
Belt feed. Some websites claim that magazines can still be used.

Shrike at Guntech
Shrike on Ares Defence site
Soldier of Fortune article on the Shrike.
Further Update
        The British Army has recently began to issue the L110 (FN Minimi/M249) on a more general scale. Not so clever is the adoption of the “Para” version with a 349 mm (13.7”) barrel giving a weapon with a much shorter barrel and lower muzzle velocity than either the L85 rifle or L86 LSW. The L86 has a barrel nearly twice the length (646mm/ 25.4”). Such a short barrel length on the L110 is likely to considerably reduce the terminal effects of the 5.56mm rounds it uses. What is interesting is that the L86 LSW will be retained. One suggestion that I've seen is that a fire team should have two riflemen, an LSW and a SAW. One of the rifles will probably have a 40mm Underbarrel Grenade Launcher. Even though based on weapons as poor as the SA-80 family such an armament offers considerable firepower which is obviously an advantage for small unit operations such as COIN. It is envisioned that the LSW have a dual role, supplementing the automatic fire of the SAW and providing long range precision fire to beyond the capabilities of the rifles.
        A M16 H-bar fitted with an ACOG sight will fill this role even more effectively, since its configuration allows the use of drums and C-mags.

        Although not based on the M16 or any other rifle the Ultimax 100 is also a good candidate for improving team firepower. Weight is only c10lbs and it can use M16 magazines. It uses a lengthened receiver so that there is sufficient internal room to prevent the recoiling bolt impacting the back of the receiver, absorbing the recoil and spreading the perceived recoil impulse over a longer period of time rather than being a sudden jolt. The forward motion of the bolt hits the barrel extension causing the muzzle to dip slightly before the next round is fired. In this Defense Review Article itis claimed the Ultimax offers an 8:1 hit-ratio advantage over the M16 rifle when both are fired offhand on full-auto side by side against multiple targets and that the Ultimax will will outhit the belt-fed FN M249 SAW and MK46 MOD 0/1 at 3-times the range, on full-auto despite being considerably lighter.
        This video seems to bear out the claims made for the weapon:-

        Latest version of the Ultimax (the Mk V) is selective fire so can fire single shots as well as full auto. Possibly an “Americanised” version that has Picatinny rails and shares components with the M16 and/or M249 could be created.

USMC trial of Ultimax, AR-15 H-bar and HK MG36 H-bar vs the M249.
Ultimax Mk4
ST Kinetics Ultimax

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