Let's summarise where we are with NGSW: 

1. BELIEFS DRIVING NGSW COMPETITION

• Need for increased range and lethality 

“Current weapons and calibres lack the required lethality growth against protected individual targets. NGSW will incorporate improved ergonomics, signature suppression capabilities, data-power transfer, new rail designs, a lightweight ammunition case and increased performance at range.” [Major Wyatt Ottmar, US Army NGSW Program Officer (October 2020)]

• Overall concept of adopting a single ammunition type used across all squad weapons offers worthwhile operational, logistical, and training benefits

• Recognition that units equipped with only 5.56x45 mm weapons will be overmatched by enemies equipped with 7.62x54 mm Russian, 7.62x51 mm NATO, and 5.8x42 mm Chinese.

• Recognition of the fact that potential adversaries using Level II/ Level IV body armour 

• Recognition by US Army that 5.56x45 mm has reached the limit of its development potential 

• Aspiration that any new ammunition option should not increase the dismounted soldier’s weight burden

• Aspiration for NGSW to provide 7.62 mm performance in a 5.56 mm package, but...

2. THE COMPETITION ITSELF

• NGSW requirement evolved into a requirement to penetrate Level 4 body armour at 600 metres

• NGSW requirement defines an ammunition standard that essentially matches .300 Winchester Magnum - a sniping cartridge

• The perception among many NATO armies observing NGSW that ammunition specification is that 6.8x51 mm is way over-powered

• Resulting muzzle energy / velocity produces significantly higher recoil making automatic fire harder to control 

• Shooting training will be more onerous, especially for soldiers of smaller stature and females

• Packing 3,000 fps / 914 m/sec performance in a 7.62-sized cartridge rather than in a larger cartridge results in very high chamber pressures (80,000 psi same as M1A2 Abrams' 120 mm gun) 

• High chamber pressures accelerate barrel wear and reduce parts longevity (requirement is 5,000 rounds, (SIG is achieving 10,000 rounds, legacy weapons deliver barrel life of at least 20,000 rounds, real issue is unexpected parts breakage)

• High chamber pressures require more complex four-piece ammunition which is more expensive to produce

• Increased system weight versus legacy 5.56 mm squad weapons adds to the dismounted soldier’s weight burden

• Larger ammunition reduces the number of rounds that can be carried for a given weight

• System through-life costs likely to be much higher 

• SIG did a great job with the XM5 and XM250 - the best option won

• The most significant element of NGSW is the Vortex XM157 fire control optic - this is superb and similar systems will be rolled-out across NATO

So, True Velocity cartridges for everything except the Special Purpose ammunition? That's what it sounds like.

And I bet Emeric could squeeze more performance out of 5.56x45 if he was allowed to.

Guardsman26 said:

4. US SOCOM IS PROCEEDING WITH ITS OWN AMMUNITION PROGRAMS 

US SOCOM has two current programmes to field weapons in 6.5x49 mm Creedmoor ; one is the MRGG the other is a LMG

?US SOCOM is fielding 6x39 mm ARC in a Geissele GFR 

The above initiatives could be a hedge in case NGSW fails to live up to expectations 

That seems illogical to me.  6.5 CM is a less capable caliber than 6.8x51, and 6.5 CM weapons are as big and heavy (or heavier?) as the 6.8x51 guns.  And it has not yet been demonstrated that an LMG in 6 ARC is even viable.

Guardsman26 said:

5. WHAT NEXT? 

?NGSW may not be fielded in as widely as expected - it may only be used to replace DMRs and LMGs in the squad 

That also seems illogical to me, if only because it would negate the "squad common caliber" rationale for adopting NGSW.

Guardsman26 said:

Expect the US Army to conduct a further study that aims to reduce the dismounted soldier's weight burden - this could yet kill or dramatically re-scope NGSW 

Sounds reasonable.

Guardsman26 said:

?Expect a new program to upgrade the M4 - this could include a gas piston operating system and even include a new calibre, like 6 mm ARC

I don't see that happening.  IMO changing from 5.56 NATO to 6 ARC has too many drawbacks, and too few advantages.

Roughly agree. The Chinese small arms family right now is really well developed along a number of different lines. New .30 Cal GPMGs that weigh ~17-18lbs. New superlight .50cal MMGs, and their light automatic grenade launchers. If any of them turn out to be duds they have a lot of fluidity to work with the others. While the US is focusing too heavily on this boomermagnum cartridge and weapons system that can't even satisfactorily replace the M4 and M249, let alone the M240.

Guardsman26 said: 5. WHAT NEXT?  ?NGSW may not be fielded in as widely as expected - it may only be used to replace DMRs and LMGs in the squad  

stancrist said:

That also seems illogical to me, if only because it would negate the "squad common caliber" rationale for adopting NGSW.

Guardsman26 said: Expect the US Army to conduct a further study that aims to reduce the dismounted soldier's weight burden - this could yet kill or dramatically re-scope NGSW 

I think that these things are entirely possible, largely because the NGSW program over-reached in the first place.  The hope was for a wonder cartridge and weapons that would weigh virtually the same as 5.56x45 and somehow be just as compact.  Now that reality has set in, it would not surprise me that the reduction in the number of rounds carried has become a concern.  

mpopenker said:

Libya 2011?

I think the US is not guilty for this one, and those who are guilty didn't invaded Libya...

nincomp said:

       Guardsman26 said:  ?NGSW may not be fielded in as widely as expected - it may only be used to replace DMRs and LMGs in the squad  

       stancrist said:  That also seems illogical to me, if only because it would negate the "squad common caliber" rationale for adopting NGSW.

I think that these things are entirely possible, largely because the NGSW program over-reached in the first place.  The hope was for a wonder cartridge and weapons that would weigh virtually the same as 5.56x45 and somehow be just as compact.  Now that reality has set in, it would not surprise me that the reduction in the number of rounds carried has become a concern.

The reduction in number of rounds carried was blatantly obvious at least two years ago when the first downselect was made.

The cartridges were clearly not going to get smaller, yet the Army continued to pursue development of both NGSW-R and -AR.

That says to me they still want a common caliber for squad weapons and are willing to accept the reduction in rounds carried.

I think the NGSW team are getting real pushback on the weight burden issue. 

However, the US Army may have been much smarter than we've given them credit for. NGSW now has three basic loadings plus tracer and blank. As I mentioned above, there is the SP round with is the armoured piercing loading that cracks Level 4 plates at 500+ metres. Second, there is a new standard loading, the GP round, which may even be fired at standard pressures and have MV of 875 mps / 2,900 fps. This would allow lightweight polymer cartridges to be used, reducing weight - but it would still be superior to 7.62x51 mm NATO in performance at all ranges due to its greater efficiency.  Finally, there is the Reduced Range (RR) loading which is designed for urban combat / CQB. So basically, units will use the GP loading in most situations, but when the threat dictates armoured piercing, the SP can be used easily and the gun will cope with it. 

If this is right, then the new 6.8 x 51 mm envelope makes a lot of sense - it can save weight relative to 7.62 x 51 mm while delivering extra range and lethality. That being the case, more NATO armies may adopt it. 

I would still prefer to see an NGSW specification that is closer to your original 6 mm Optimum cartridge, Stan. Put a bit more energy behind a VLD 6 mm projectile with a mass of 95-110 grains (6 or 7 grams) and you'll have a very flexible, lethal ammunition that exceeds 7.62 mm at all ranges while being close in weight to 5.56 mm. The trick is a base diameter small than 7.62 mm, so you can carry more rounds for a given weight. 

Guardsman26 said:

I think the NGSW team are getting real pushback on the weight burden issue.

That does not surprise me in the least.  I expect the pushback will increase after units are equipped with the XM5.

Guardsman26 said:

However, the US Army may have been much smarter than we've given them credit for. NGSW now has three basic loadings plus tracer and blank. As I mentioned above, there is the SP round with is the armoured piercing loading that cracks Level 4 plates at 500+ metres. Second, there is a new standard loading, the GP round, which may even be fired at standard pressures and have MV of 875 mps / 2,900 fps. This would allow lightweight polymer cartridges to be used, reducing weight - but it would still be superior to 7.62x51 mm NATO in performance at all ranges due to its greater efficiency.  Finally, there is the Reduced Range (RR) loading which is designed for urban combat / CQB. So basically, units will use the GP loading in most situations, but when the threat dictates armoured piercing, the SP can be used easily and the gun will cope with it.

I don't see any of that as being unusually smart.  The GP and SP loadings are not new developments; they've been planned pretty much since the beginning.

The RR loading is recent, but what I've read is that it was developed to cope with GP ammo exceeding the limited danger area on ranges, not for MOUT/CQB.

Guardsman26 said:

If this is right, then the new 6.8 x 51 mm envelope makes a lot of sense - it can save weight relative to 7.62 x 51 mm while delivering extra range and lethality. That being the case, more NATO armies may adopt it.

I would rate the weight saving relative to 7.62x51 as negligible, but I agree that more NATO armies may like the extra range and lethality enough to adopt 6.8x51.

That is assuming the US Army follows through and fields the system, of course.  There's the possibility that XM5 and XM250 could go the way of XM8 and XM235.

More deflection.