.50 Machine Guns

Ralph Zumbro:-
        If you have an M-2 Browning in a mount with optical sights, you own one of the world's most effective sniper weapons. AND it doesn't take Carlos Hathcock to use it. There is quite a few tons of stability under that sight.
         Hit the bolt release and fire from a closed bolt, and I guarantee that you can hit a man at half a mile. With practice you can also flatten a tire. The name of that trick is "ballistic surgery".

        Optic scopes help you see a target better, not make you a better shot, so it is possible to perform such shooting with the iron sights. A lot of Ralph's shooting has been done with vehicle mounted .50s, both M2s and M85s, hence the "few tons of stability".
        Field Manual 3-23.65 gives the Maximum range of the .50 in excess of 6,760m, Effective range against area targets as 1,830m and against point targets as 1,500m for single shot fire. Range against a point target with a 6-15 round burst is given as 1,200m.
        FM 3-23.65 details how to use the .50 MG for single shot long range shooting:-

Section 3-2

Single-Shot Mode.

        One thing that is noticeable about US forces is the wide availability of the .50 Browning heavy machine gun. Every vehicle seems to have one, including rear echelon vehicles such as supply trucks.
        The .50 bullet is rightly feared and respected. A .50 can pass right through a LAV lengthwise and exit the other side. Fired from a tripod or stable vehicle mount the weapon is accurate enough to snipe with out to at least a thousand yards.
        The BHMG is well loved by GIs and famed for its power and relieability, so when I was reading Cameron Spence's book "Sabre Squadron" I was a little surprised on the SAS's opinion on the M2 Browning. Most of the comments are not repeatable in polite company, but the gist was that they didn't ask whether the M2 would jam or not, but when?
        Turns out that being a recoil operated weapon the M2 is rather sensitive to having a correctly adjusted headspace. Ammo variability can also have an effect.

Ralph Zumbro:-
        Subj.50; If the sucker jams, run the headspace IN 5 clicks, hit the charging handle. Back it out till it fires. Give it one more for safety. Headspace changes as the gun heats up. You can eliminate ALL problems by using the aircraft .50 barrel. The sad thing is that we learned all these lessons in RVN and were/are ignored by the Pentagon.

        I began to wonder if a new .50 calibre machine gun might be possible –maybe based on the lightweight 30mm ASP cannon. A lighter weapon than the M2, possibly with dual feed would be nice.
        Dual feed is a good feature for a HMG to have. It allows one belt to be loaded with ball and tracer while another is loaded with an anti-vehicular mix of SLAP (Sabotted Light Armour piercing) and APHEI or HEI. For the latter a good choice is Raufoss of Norway's multipurpose NM140 with a hard core and RDX filling. This will penetrate 11mm of armour plate at 1000m then fragments to deliver incendiary particles up to 15m behind
In fact such a weapon already exists.

http://www.st.com.sg/cis/fiftymg_main.htm

http://world.guns.ru/machine/mg05-e.htm

The US is probably supplied with enough M2s to last it quite a while, but it would be nice to see this lighter weapon available to infantry units. These could be moved more easily by hand carts or wheeled mountings.
The UK doesn't use heavy machine guns as standard issue, but certainly needs them, and it would be nice to see them adopt the CIS 50. (Apparently the British Army does now own some BHMGs, some of which I suspect had one previous owner, manuals in Spanish...)

More on the CIS 50

        The OCSW is supposed to replace both the .50 and the Mk-19, but I think that it is unlikely to entirely replace the HMG. The .50 is a better weapon than the OCSW for fast moving targets or for firing from aircraft where there is a high relative speed between the platform and target. It also produces less collateral damage than an exploding 25mm grenade. In the past I've suggested a saboted KE round for the OCSW but conventional .50 ammo will bulk less and a dedicated weapon can incorporate dual feed.
        It may be possible to create a .50 weapon sharing many of the components of the OCSW and of similar weight. I'm obviously not the only one to come to this conclusion. A .50 calibre machine gun based on the OCSW is being developed. The General Dynamics site also mentions that the 25mm OCSW XM307 can be converted into a .50 HMG.
        The General Dynamics XM312 has a cyclic rate of only 260rpm so is not considered suitable for air defence applications. The Chinese have already fielded the 12.7mm QJZ89 HMG which weighs only 26kg including tripod. This offers a cyclic rate of 450-600rpm and is suitable for all likely applications. According to this site the Weapons Companies of some Chinese Army Infantry Battalions are intending to use the QJZ89 instead of 7.62mm GPMGs.
        An interesting comment on world.guns.ru reports that the Kord 12.7mm HMG can be used from a light bipod when mobility and damage are a priority over range.

Further on KE rounds for the OCSW.
         The OCSW has a proportionally short case so a sabotted 12-16mm bullet is probably not practical mounted in that case. A longer case that mounts a saboted KE round and gives the same overall external dimensions as the 25mm grenade round should be possible.

        If you want a high velocity weapon with explosive airburst capability it would probably end up resembling the 30mm ASP cannon. Programably primed 30mm cannon shells are being tested already, so the weapon probably will be an ASP with a fire control unit. 30mm "mortar" loads for high trajectory shots have also been experimented with.
        The ASP is still a little heavy to carry any distance so the infantry will probably mainly use the OCSW. Since the OCSW loads by "cans" rather than a belt it should be possible quickly change to WP rounds for a smoke laying mission. Each battalion should, however, retain a squad with four .50 HMGs, configured for both ground and airborne targets.
        For vehicle use a OCSW is probably light enough to be mounted alongside a HMG, particularly if the HMG is a model lighter than the traditional HMG. The laser rangefinder in the OCSW fire control module will also be useful for machine gun fire. Since the OCSW is loaded with HE and "AP"(HEAT) the HMG can be a single feed model loaded mainly with ball ammunition.

Ref

Raufoss Ammo.

Another site on Raufoss MP rounds

SLAP rounds

.50 Ammo.