In 40x46 mm LV, the "low pressure" chamber is around 20 MPa, and proof pressure is 23.5 MPa if I remember well.

A recoilless system springs to mind

Or maybe a modern day "PIAT" in 40x53 with airburst capabilities?

Might be a bit inaccurate due to the pre-shot-recoil, but at this modern day, counter-rotating gyroscopes should be a possibility.

Spin them up by touching the trigger, and brake them by releasing the trigger.

With the advent of options like 40mm pike and weaponized drones small enough to be used at squad level, it seems like a solution in search of a problem.  Things really are going to get very lethal very quickly over the next few decades.

Drones will be jammed by ir-smoke and lasers and other counter-measures.

If a nuclear nation is attacked by another nation, that is overwhelming them by weaponized drones, they may get nuked. If they attack with autonomous weaponized drones, they WILL get nuked.

Fully autonomous recon-drones will probably be accepted, but jamming will probably hinder live communication of images.

And that  means personnel will have to be close to the action, and possibly do a lot of the fire-fighting themselves.

Of course, that is in a major international war. In smaller regional wars, and civil-wars, humans will do most of the fighting, unless fighting against a major power. Like when Turkey used Aserbadsjan as a proxy against Armenia. 

One of the interesting things about 6.8 is its potential effect on HE weapon systems. 

Given the ~12lb weight of the 6.8 rifles once the smart optic is factored in, adding a ~3lb underbarrel grenade launcher would bring the weapon weight to 15lbs - about the same as the Milkor M32 with optic. That means that the collective weight should be high enough to fire Medium Velocity grenades without any need for a recoil dampening system. And the laser range finder and ballistic calculator of the NGSW FCU already provides most of the raw materials for a grenade launcher FCU...

On the flipside, by having a 6.8 LMG at the squad level, theres suddenly much less need for a GPMG 'weapons squad.' This offers the tantalizing prospect of reconfiguring the Weapons Squad from GMPG's to HE slingers - either an Airburst AGS-30 type system, the Imortar 60mm with FCU, or Carl Gustav's with airburst / guided rounds. 

Your weapons squad still needs GPMGs because the best position to support and overwatch your maneuver element is rarely with the maneuver element, and if they are with the maneuver element they're slowing everyone down (a bit of a moot point in places like Afghanistan since everyone is loaded down like mules moving to contact with approach loads anyway, but that will get you killed against a competent enemy)

I think the GPMG will be supplanted by the LWMMG in the weapons platoon. And maybe a 51mm recoilless gun? 

Well, the US Marines are going to 84mm for every platoon..

Farmplinker said:

Well, the US Marines are going to 84mm for every squad.

FIFY.   ;^)   https://youtu.be/jfVxspzh0Pg?t=75