autogun said:

There are some interesting wrinkles in the question of swapping around between guns and ammo. As I understand it, the longer barrels of the GD bullpups mean that their TV ammo can achieve the same performance at lower chamber pressures. The SIG's ammo is therefore likely to have a hotter loading, which the GD might not do so well with. OTOH, the TV ammo might not deliver the performance required if used in the short-barrelled SIG carbine. The CT gun and ammo designs are of course incompatible with everything. Interesting that they are still saying nothing about the MV requirement (in fact, they no longer seem to be mentioning any body armour penetration requirement, even though that was supposed to be the main driver). The interior ballisticians among you will have to keep your calculators on stand-by for a bit longer!

Yes, the (likely) lower pressure of the .277 TV is why I see the .277 Bullpup + TV case + SIG 6.8 LMG as the most likely crossover. 

-Lightweight cartridge ( ~15.5g TV vs 21g for SIG)

-3,000fps ballistics from carbine (vs 2850fps for SIG carbine with SIG ammo)

-SIG 6.8 provides belt fed LMG ability (vs absurd 20rd box fed of GD)

The 6.8 LMG would need to have its barrel lengthened from 16" to 20", which is not ideal. However, given the length of the SIG suppressor, vs the shortness of the Brevis used by GD, I suspect the overall length increase to be below the 4" barrel change. 

Whereas, with the lower pressure, using the .277 TV as a crossover with the SIG Carbine seems very unlikely, as it would likely not get enough velocity from the SIG's 13" barrel. 

stancrist said...

Ditto.  But, a more visually-appealing suppressor wouldn't help with other aspects of the design.

- Bullpup configuration.

I quite like the aesthetics of a bullpup rifle, so that’s not a negative for me. I understand that others hold strong opinions on it though.

stancrist said...

- Stock not adjustable for LOP.

I’ve never been convinced that LOP is an issue for flat-topped rifles with long sight rails.

stancrist said...

- Magazine-fed automatic rifle.

That I agree is a negative. Someone would have to remind me on the difference between a Light Machine Gun and an Automatic Rifle before we get hung up on the subject of what’s best for a squad automatic.

I see that I'll have to do a "reverse" weight reduction plan to show how stupid this all is.

Usually, LMG=belt-fed and/or quick-change barrel; AR= mag-fed and "fixed" barrel. That's my personal rough and dirty definitions. YMMV.

RovingPedant said:

I quite like the aesthetics of a bullpup rifle, so that’s not a negative for me.

Ditto.  Personally, I love the bullpup concept.  I'm just skeptical that the US Army will go for it.

RovingPedant said:

Someone would have to remind me on the difference between a Light Machine Gun and an Automatic Rifle...

I'm not sure if there is a consensus.  When talking about modern weapons, I see it basically the same as Farmplinker:

LMG = belt-fed

AR = mag-fed

RovingPedant said:

I’ve never been convinced that LOP is an issue for flat-topped rifles with long sight rails.

I don't know if it actually would be a problem or not.  But it looks like it could be, depending on the optic used.

Assumptions are 140 rounds per gun for all the NGSW rifles, 1,000 rounds per gun for the NGSW belt feds, and 220 rounds per gun for the GDOTS mag-fed AR.

You posted the reduced load elsewhere but I can't remember it - memory isn't what it once was...

https://mega.nz/file/C1k10KCY#X--1B70RNllc0nDKhyZmuRnDK6PtH-IDrJ9Eey86sxY

So is it accurate that most of the weight savings for the GDOTS combo comes from a sharply reduced ammo load for the AR/LMG?  

How are the Marines loading up their AR gunners with the M27?  Just a 30% increase like you're calculating for the GDOTS AR?  

taschoene said:

So is it accurate that most of the weight savings for the GDOTS combo comes from a sharply reduced ammo load for the AR/LMG?  

Yes. I have them carrying 1,420 rounds per squad, instead of 2,980 rounds for the other two.

taschoene said:

How are the Marines loading up their AR gunners with the M27?  Just a 30% increase like you're calculating for the GDOTS AR?  

Correct. 11 magazines (330 rounds for the M27, 220 rounds for the GDOTS NGSW-AR).