The Army is moving forward with polymer 7.62x51 ammo. This is a surprising albeit welcome development given the NGSW program and its use of metallic cases. Also surprising that PCP would beat True Velocity for the contract. 

https://soldiersystems.net/2022/06/10/pcp-tactical-selected-to-produce-lightweight-polymer-cased-ammunition-for-the-u-s-army/

If this comes to fruition, we could see a rather bizarre situation where 7.62 PCP is actually lighter then the new 6.8 NGSW ammo. 

hopefully 6.8x51 hybrid polymer will be adopted at some point

Eagerly awaiting production overruns to try in my .308 Garand....

I suppose that means that True Velocity ammo did fail to hit some kinds of standards then.    

Although its odd that they'd beat out PCP in the NGSW trials earlier, only to lose here later. Perhaps it came down to cost over anything else.

"The M240 machine gun is the primary weapon for this effort [...]"

So, 6.8x51 mm conversion kit and now polymer case M80A1 for the M240... the US Army really wants lighter stuff, no matter what it is!

Yeah it seems a bit divided / bizarre to be doing this now with 6.8 NGSW (along with other request for 6.8 M240 conversions a few months ago.)

Plus of course now that we're out of A'stan and pivoting to Near Peer HIC, the rationale for lightweight ammo for extensive foot patrols seems less pressing. 

gatnerd said:

Yeah it seems a bit divided / bizarre to be doing this now with 6.8 NGSW (along with other request for 6.8 M240 conversions a few months ago.)

What you characterize as divided/bizarre, I'd call prudent planning which shows that somebody in Army leadership has paid attention to history. 

It is not absolutely certain that the XM5 and XM250 will be fielded.  Remember previous XM-series weapons, like the XM8 (carbine and light tank)?

gatnerd said:

Plus of course now that we're out of A'stan and pivoting to Near Peer HIC, the rationale for lightweight ammo for extensive foot patrols seems less pressing.

We've been here before.  For half a century after WWII the Army's focus was on HIC.  What types of conflict did the Army actually do?  LIC and COIN.

And even in the seemingly unlikely event that HIC against a (near) peer opponent should happen, lightweight ammo would be beneficial for logistics.

I wonder if the reduced-range ammo for the new 6.8x51 will be loaded in polymer cases at some point.  There has been some speculation that the new 6.8 Carbine would use the reduced range ammo for combat as well as practice.

Then again, True Velocity claimed that their polymer cartridge could handle 80,000 psi.  The bottom of the cartridges are made of metal already.  I wonder if PCP could make full-pressure 6.8x51 ammo as well?

nincomp said:

I wonder if the reduced-range ammo for the new 6.8x51 will be loaded in polymer cases at some point. 

It definitely will be.

Maybe.  Maybe not.

It will never happen.

One of the above is probably right.  

nincomp said:

There has been some speculation that the new 6.8 Carbine would use the reduced range ammo for combat as well as practice.

Is there a sound, logical basis for that speculation, or is it just random internet guys saying, "Hey, why not use the reduced-range training ammo for combat?"

It seems to me the Army would want to use ammo with the GP bullet for combat, not a special projectile designed to limit maximum range for target practice.

There is no technical reason why a lower-powered GP round could not be developed for door-kickers.  The extra penetration may be considered a liability in an urban environment and reduced recoil and reduced weight (with a polymer case) would address commonly cited disadvantages of the new weapon system.  Cost would also be a factor because the hybrid cases will not be cheap.  A GP round at lower pressure would increase barrel life as well.

There is more than one type of reduced range ammo.  One option would be a version of the GP load at lower pressures, possibly using a higher-drag projectile.  Since the new weapons will have a programmable optic, it is no longer so important for the reduced-range projectile to match trajectory of full power combat ammo out to several hundred meters.  As you are probably aware, some current reduced-range ammo use fins or flutes designed to slow bullet rotation and cause instability after a certain distance.  If desired, of course, this type of ammo could be produced as well.