I don't know about the US army, but could you be more specific Herald, concerning the type of machine gun?

 

LMG/GPMG/HMG/GMG... they all are needed, or at least desirable.

On my own limited knowledge, I would suggest:

Near term would be improved optics, possibly electro-optics like thermal imagers

The thing is, for a GPMG, you really want it to be effective in the light role as well (off a bipod), so mass reduction and a matching recoil attenuation system would be sensible. Possibly a variable rate of fire depending on the role you intend it for. For aimed fire, you want a high rate of fire so as to increase the chance of a hit before the target takes cover, for area you would want lower, so as to maintain suppresion for longer with the same ammunition load.

In an ideal world, a method for feeding like a belt without the attendent fouling problems would be nice.

Fire arc is a function of weapon mount.

There will be almost no improvement can be done to current M240 unless there is an innovation in ammo technology.

 

Say, the bullets that can find and identify targets by itself like the one you saw in Fifth Element. That will be great if it can be done. Other options including liquid propellent, so that the loader only need to carry bullets and propellent tank. But it doesn't sound like a good idea, because it will be not only messy, but also suicidal to carry liquid propellent containers into the fields. Caseless and telescopic ammo don't provide much advantage to current generation ammunition. Caseless ammo do not have brass to carry away heat, though if liquid cooling system can be fit, like M1917 machinegun, it could be good idea. This is not so good to people who have to carry big water tank, though. If Ghostbuster's proton generator can be manufactured, then probably we can issue portable rail-machineguns. Yeah, If it can be done, people might try to make a flux capacitor as well.

Perhaps to the aiming systems?  Just a guess....

One possibility would be to move to a lighter-weight general purpose machinegun, e.g. the Mk48, especially if there were a switch to a lighter calibre (allowing a uniform standard calibre, perhaps something like the 6.5mm MPC). There could then be a lighter alternative to the .50cal, e.g. the .408 CheyTac, to work alongside either the Mk47, Mk19 or XM-307. The main aim would be to lighten the overall load - if a case telescopic rounds can be made available, a 7.62mm equivalent round could probably be designed to be more like the 6.5mm for weight. If we can therefore switch to a uniform series of calibres, i.e. case-telescopic 6.5mm round for the dismounted infantry, and a heavy-ish machinegun in .338 or .408 for vehicle use. In both cases it allows a much lighter ammunition load, hopefully not hurting actual combat capability either, especially if combined with the various 25mm weapons.

This to my mind, along with the  feed extract problems has been the big  engineering problem to making a reliable machine  gun. What do you doi about the heat burden that deforms the  fit of the machione gun and interferes with its cyclic operation as well as prematurely cooks its ammunition?

If caseless and telescopic ammunition does not  transmit heat with as much efficiency as brass, what are the proposed solutions?  I know that some proposals involve a revolver  mechanism design to rotate combustion chambers in series to allow cooling between shots, but is this practical in a light machine gun? How much fouling will such a mechanism introduce into what is already a dirt sensitive mechanism?

Herald

I didn't think of the revolver design. Thanks for reminding me about that. M39 20mm cannon is revolver design. There is nothing fundamentally wrong with it, though feeding is abit complex. I've heard that Russians have some gas-driven revolver cannon. This idea may be used on a 7.62 marchine gun. As far as I know, an experimenting LMG is designed with revolving chamber and telescopic/caseless ammo. Fouling may or may not be an issue depending on revolver design. If you design the telescopic case right, the case can seal and be supported by the chamber. However, I really don't see how it would beat M240. M240 is heavy, elegant and remarkably simple piece of machine. You can't really top that design without some voodoo magic. OK, maybe PKM in 7.62NATO can, but that's another story.

 

Current generation use open bolt and barrel-change capability to battle heat problem. It is thermal dynamics, and you can't win. Water cooling is more efficient, and that's why those old German MG08 and British Vickers can shoot all day if John the private second class keeps the keg full of water.

In my humble opinion, the best way to suggest improvements is to address the shortcomings of modern general purpose machine guns.  First of all, they are heavy.  Anyone that has "humped the pig" (which was a reference to the old M-60) knows that lugging that thing around can be a pain.  Throw on a few hundred rounds, and it becomes a real bitch.  I would look at ways to reduce weight by using space age polymers and finding ways of making the metal components from strong, yet lightweight metals.  To further reduce weight I would try to eliminate the links on the ammunition belts, and the best way to do this would be to go with caseless ammo.  Ammo could be carried in 100 rd. waterproof sealed "cassettes", which would keep the ammo clean and dry, and would be easier to carry than loose belts or ammo cans. 

 

Reducing weight in automatic weapons, however, could be problematic because weight makes recoil a little easier to handle.  Already weapon designers are working on submachine guns with systems that are practically recoilless.  I would look at ways of applying these systems to general purpose machine guns.  Low recoil in a machine gun would make it more accurate, particularly when it's being fired from a bipod.  Good optics would enhance this accuracy.   

 

An age old issue with machine guns is that after a few hundred rounds they get hot-----too hot to touch.  If it's true that caseless ammo burns hotter than brass cased ammo (which I found interesting), then I would look at ways of cooling the weapon.  I would once again look at ways to use metals and polymers that can handle the heat, but I would also examine ways of doing this chemically, maybe by installing tubes containing some sort of cooling liquid that would be heat activated.  When the weapon fired the tubes would begin cooling the barrel and handguard.  I may have just dropped off into sci-fi land there, but it just came to me.  I'm a knuckle dragger, not a scientist.

 

A variable rate of fire would be an absolute must.  I would set a low rate at around 500-600 rpm, and a high rate at 900-1000 rpm, maybe a little higher.  The system would also need to be modular and adaptive to a wide range of needs.  It would have to have the quick ability to be fitted to vehicle mounts, tripod mounts in the crew served mode, fired from a bipod, or carried by one man and fired from the hip like the proposed "trench broom" of WWI (the way John Browning foresaw his BAR would be used).  It would be nice if this could be done without tools, if possible. 

 

Speaking of sci-fi, I would also like a digital display like the one the Colonial Marines had on their guns in Aliens so I would know how many rounds I have left............but this is purely optional. 

You are a freaking genius! This is absolutely viable using technology we know. Though chemical means imply that some disposable cooling jacket must be carried in addition to weight of the gun and ammo, it nevertheless opened another possibility.

As for round counter, it can be done pretty easily. Why it hasen't been done is out of my knowledge.

I think what you actually want is a Heat Pipe and a large radiator.

 

As for a cooling media, water is still the best.  It takes more energy to evaporate/boil a pound of water than any other commonly available substance.  The trick for modern materials is to make a cooling jacket that cannot be fouled when using recycled water (i.e. urine).