+ 1.5 lb optic (probably idk)
+ 0.5 lb peq 15

gee that is one heavy loadout

5.56 fabrl Magnum sounds lovely

I think the optic is closer to 2 - 2.5 pounds.

The gun will definitely be heavy.

Hell even my 16" 5.56 gun with 34mm mount and large tube 1-8 plus bootleg peq15 alike is not light.

Is it workable?

Yeah sure, but when people are already going to slingster style padded slings to spread the load of their 5.56 rifles including me it definitely says that even fully kitted 5.56 m4a1's are probably heavier than is really ideal.

Could this change if guys weren't averaging 100+ pound individual combat load outs?

Probably.

Rifle and ammunition weight doesn't exist in a vacuum and I think that we're about to find this out in a big way.

EmericD said:

       stancrist said: No, you absolutely do not need another weapon. You only need another barrel, one that has the correct rifling twist for the bullet.

The US didn't adopted a "M16A1 with a new barrel", they adopted the M16A2, which is another rifle.

Yes, that is quite true.  However, the M16A2 does not just have a different rifling twist than the M16A1. 

The M16A2 differs from the M16A1 in that numerous changes/improvements  were made to the design.

- New buttstock

- New pistol grip

- New upper receiver w/new rear sight and case deflector

- New lower receiver w/3-rd burst control

- New barrel configuration

- New fore end

- New front sight post

- New flash suppressor

Except for the caliber, the M16A2 was an almost completely different rifle than the M16A1.

EmericD said:

It's plain and simple, the M16A1 can't fire the SS-109 ammo...so you can't consider that "it's just another loading".

You're wrong on both counts.

a.  Like M193, the SS109/M855 is "just another loading" of 5.56x45 ammo.

b.  The M16A1 can fire SS109/M855 ammo (but accuracy is unacceptable).

EmericD said:

       stancrist said: 5.56x45 is still 5.56x45, whether loaded with 55gr bullets or 62gr bullets (or any other weight).

The boxes you show are written ".223 Rem" and not 5.56x45 mm.

Yes, because -- like 5.56x45 -- .223 REM is .223 REM whether loaded with 55gr or 62gr bullets.

But if that minor detail is of such great importance to you, here are cartons labelled 5.56mm:

EmericD said:

       stancrist said: I did not say NATO adopted 5.56 "to please" the US. I said NATO adopted 5.56 because it was a standard US caliber. The only reason there was NATO interest in 5.56x45 was because the US had adopted and was using that cartridge. If 5.56 had never become a US standard caliber, it's extremely improbable that NATO would have wanted to adopt it.

As the US is the main driver behind NATO, and forced the initial adoption of the 7.62 x 51 mm (against the will of a significant number of NATO countries) in 1954, only to adopt the .223 Rem less than 10 years after (and without any considerations to other NATO countries), I think that it's not arguments, but self-fulfilling prophecy.

Call it "self-fulfilling prophecy" if you like, but the fact remains that the only reason 5.56x45 was adopted by NATO is because it was a US standard caliber.

The Belgians would never have developed the SS109 loading if 5.56mm had not been a US standard caliber.

roguetechie said:

Rifle and ammunition weight doesn't exist in a vacuum and I think that we're about to find this out in a big way.

It should prove interesting. 

I see they apparently dropped the original 210-round basic ammo load nonsense. 

That helps a little with soldier carry load, but at the expense of combat endurance.

Yes, combat endurance is something that's a very key interest of mine.

In the case of the machine gunner load 4 100 round nutsacks is probably ok but the rifleman load seems pretty lacking to me personally.

In the case of machine gunners, the ability of 6.8 to turn cover into concealment versus the 5.56 m249 it ostensibly replaces is likely extremely worthwhile.

I personally think pairing 6.8 belt feds and DMR's with 5.56 carbines could be workable but doing both the rifleman and gunner seems like combat persistence will take a dangerous hit.

End of the day the future is in the new optronics , 6.8 makes no sense if you don't drastically up the hit probability with optronics, but then again optronics alone would also drasticaly increase 5.56 and 7.62 effectiveness.

New upgrades to gear over the past 2 decades came with a considerable weight penalty,and the only weight they saved was by cutting the barrel down, even on bullpups its all 16in and shorter barrels. IT seems like today's soldiers even with 5.56 barely carry any more ammo than they did 7.62 in the past.

stancrist said:

Except for the caliber, the M16A2 was an almost completely different rifle than the M16A1.

That's what I wrote.

The US did adopt another rifle along with the (then) new 5.56 x 45 mm.

stancrist said:

You're wrong on both counts. a.  Like M193, the SS109/M855 is "just another loading" of 5.56x45 ammo. b.  The M16A1 can fire SS109/M855 ammo (but accuracy is unacceptable).

No, Sir, plain and simply.

Issuing SS-109 / M855 ammo to soldiers equipped with M16A1 would be a bad joke during training, but it would be lethal during combat operation.

As you know, soldiers, unlike some civilian shooters, don't use their guns only to make noise and entertaining videos on Youtube.

The picture you're showing could be misleading, as the dispersion depends on the temperature.

With air temperature above 32°C, you could stabilize the SS-109 in barrels with a 1-in-12" twist and see only a slight reduction of the accuracy.

With air temperature around 21°C, you will find the reduction of accuracy shown in the diagram.

With air temperature below 0°C, you won't be able to get all your shots in a 2 m x 2 m square target above 100 m.

"5.56 x 45 mm" ammo is defined by the STANAG 4172, what manufacturers do for civilian applications is of poor interest.

stancrist said:

Call it "self-fulfilling prophecy" if you like, but the fact remains that the only reason 5.56x45 was adopted by NATO is because it was a US standard caliber. The Belgians would never have developed the SS109 loading if 5.56mm had not been a US standard caliber.

Sir, no Sir.

When the SS-109 was selected, there was not a single US rifle (or weapon) able to use this ammo.

If the goal was "to adopt the standard US caliber", then NATO countries would have selected the M193 or the proposed XM777 (compatible with the M16A1), and they didn't.

All the tests were performed "against" 7.62 mm control weapons, and the SS-109 was the only SCHV cartridge able to defeat a "10 gauge" plate at a range similar to the 7.62 mm ball ammo (>550 m), all others fall short of that requirement.

The fact that it used the same case than the US .223 Remington was a wise move from the Belgium side, the UK followed a similar path with the 4.85 x 49 mm. By the way, some M16 were transformed to fire the 4.85 x 49 mm, it was just a barrel (and buffer) swap, just like the SS-109.

So, NATO adopted the round that delivered the best performance (by large and far) and the US adopted a new rifle to fire it, and history would have been similar in case of a UK 4.85 x 49 mm "victory". NATO would have adopted a new round, and the US a new rifle.

Given the failures of a lot of superscopes in the last decade, I don't have the highest hope for this new NGSW FC either. The French already mostly did the same thing with their Felin project, and we can see how well that went.

EmericD said:

       stancrist said: Call it "self-fulfilling prophecy" if you like, but the fact remains that the only reason 5.56x45 was adopted by NATO is because it was a US standard caliber. The Belgians would never have developed the SS109 loading if 5.56mm had not been a US standard caliber.

Sir, no Sir. When the SS-109 was selected, there was not a single US rifle (or weapon) able to use this ammo.

???  You lost me.  You seem to be objecting to my comments, but I don't see how your statement relates to what I said.  

Is there reason to think the SS109 loading would have been developed if 5.56mm had not been a standard US caliber?

EmericD said:

If the goal was "to adopt the standard US caliber", then NATO countries would have selected the M193 or the proposed XM777 (compatible with the M16A1), and they didn't.

At the time, 5.56x45 had been a US standard caliber for years.  M193 was the US standard Ball loading.

5.56x45 was adopted by NATO as a standard caliber.  SS109 was made the NATO standard Ball loading.

NATO adopted the same caliber as the US, but opted for a different loading.

ETA:  Note the caliber is the same for both the M16A1 and M16A2:  5.56mm.

EmericD said:

By the way, some M16 were transformed to fire the 4.85 x 49 mm, it was just a barrel (and buffer) swap, just like the SS-109.

a.  So you're admitting that I was right, that only a new barrel was needed to use the SS109 loading?

b.  How did the Brits manage to make a cartridge with ~0.2" greater OAL fit into the M16 magazine?