So anyways, I'm thinking
40mm Bofors and
30mm rounds will overtake the 25mm chaingun essentially, and that it will be possible to mount a chaingun on the top of the vehicle without seriously extending in to the cabin. There's a few designs out there, such as the
Pandur II or
Iveco Super AV (which was officially adopted by the marines), which extends only slightly or not at all in to the Cabin, with the Pandur allowing for 12 passengers and the IVECO 10 with the remote operated turret. And yes, remote operated turrets are much smaller than manned turrets, just as they'd be on tanks (with a manned turret only allowing for 8 passengers, instead of 10). The Pandur II provides the greatest turret maneuverability but low protection, and the Iveco provides greater protection but less maneuverability. The
FNSS PARS is another option, but it's currently way over budget and slightly less effective. Both systems offer good anti-aircraft capabilities, particularly against helicopters, with various missiles potentially mounted next to the chaingun. The air-bursting chaingun ammunition also allows to defeat enemies hiding behind walls, around obstacles, or simply to pepper a wider area, with it being much easier to hit the target with a wide area of effect. The higher power also allows it to pierce the armor of most IFV's or APC's, unlike a .50 caliber machine gun. The secondary machine guns will of course be good for infantry support, while the main guns are good at fighting enemy infantry and aircraft, as well as supporting infantry against hard to reach targets, like behind large barriers or inside of buildings. It also allows for an easy time working with tanks, like the 25mm chaingun of the Bradley. Considering the massive firepower and strategic advantage of it, I think it will be a pretty big shift. The ability to provide a curtain of fire against aircraft will deter aircraft simply bombing APC's to pieces, or other vehicles nearby like tanks, while simultaneously allowing for the ability to defeat the armor of most other APC's. The air bursting capabilities will be great for defeating infantry, as well as infantry that are in hiding, and given how easy it would be to add to virtually all APC's, there doesn't really seem to be a reason not to use it. In large numbers it's even more useful, and would become an important element to strategy for both anti-air and infantry fighting purposes. You'd cut down on the number of vehicles you'd needed for different roles, and the same vehicles could theoretically also support tanks.
Anti-missile systems which shoot down missiles, like the
iron curtain system, will protect against RPG's. Due to the high reliability and broad range of missiles it can defeat, it seems like standard anti-tank weapons will essentially become obsolete. Instead I imagine kinetic energy missiles, like the patriot missile, traveling at like 1500 m/s will be used instead. If you look at a javeline missile, it already accelerates a 20 or so pound projectile at 750 m/s, and if you halve the range you could get about 1500 m/s, or if you increased the rocket power. With a roughly comparably sized missile, say equivalent to an M1 abrams tank round, you'd have the same velocity and therefore power from the same sized projectile, but be able to penetrate through heavy tank armor and avoid being shot down by a system largely designed to destroy the electronics of the oncoming missiles. Titanium armor is likely to become more common, being more corrosion and heat resistance, and 40% lighter than steel, while being around the same strength. Titanium is only 15% more expensive than armored steel right now due to new manufacturing methods, and like the M777 Howitzer or M240L, the military is starting to use more titanium.
As for the infantry themselves, they'll probably use more compact, shorter guns with faster burning propellant allowing for shorter barrels, like the
M855A1 or 6.8mm Remington, and potentially the
LSAT caseless or telescopic polymer rounds. The LSAT machine gun for example, at a mere 10 pounds vs. 17 pounds for the M249, with the same reliability and ammunition that's half the weight, could allow the individual to carry 25 less pounds of gear for the same load-out (10 pounds + 15 pounds for 1000 rounds of ammunition, vs. 17 + 31-33 pounds), with a gun that's just as reliable and has less recoil. Considering that the U.S. marines are moving towards the
M27 IAR concept to replace the standard M249 machine gun in most situations and the military is looking for a one size fits all firearm, The
marines are also shifting towards arming all soldiers with suppressors and other equipment typically reserved for special forces units, particularly to enhance room clearing, and other units are following suit. The emphasis is also on low drag bullets, which have a longer range and greater overall power. The 6.5mm creedmoor or rounds like it are increasingly more popular, like in the LSAT program or with the
special forces adopting the 6.5mm Creedmoor.
Rifle resistant helmets are becoming a thing, with the
AS-600 capable of stopping a 7.62mm NATO or ak-47 cartridge, and the
ECH supposed to be able to stop various unspecified 7.62mm rifle rounds. Considering that is it heavier than the AS-600, uses stronger dyneema with a reinforcing matrix a carbon fiber backing, I'm guessing it's at least as strong. The AS-600 has a V0 of 640 m/s with the 7.62mm NATO, but the V50 is higher. At long range at least it can stop rifle rounds, which is quite impressive. Full body rifle resistance will be rare, as will exoskeletons, but is theoretically possible. If you take the weight of the armor, covering about 1.3 square foot of surface area, and remove the weight of the chinstrap and inner lining (about .6 pounds), that gives about 2 to 2.5 pounds of weight per square foot, and if covered over the 20 square foot of the body, or 40-50 pounds to be rifle resistant which is, honestly not bad. Exoskeletons like the HULC might be used in machine gun teams, particularly if combined with cooling suits or oxygen concentrators, but time will tell. Anyways! This is just some observations, and it's going to be interesting to see how things turn out. We are in a turning phase right now where equipment is actually being upgraded, and in similiar manners all over the world, sort of like when assault rifles and battle rifles were adopted.