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NGSW Phase 2 Consolidation and info   Small Arms <20mm

Started 30/8/19 by gatnerd; 477825 views.
poliorcetes

From: poliorcetes

30/10/21

1. Excuse me for the question, because probably it has been made more than once here but my memory fails just too much lately. Why do you think SiG decided for a steel + brass case instead of a pure steel one? I assume that there is a reason that compensates higher expenses and complexity but I cannot figure it out

2. If M1186 design ends into a "broad belt" factor (belt as the part of the bullet that is in full contact with the bore, I don't recall the name in English), even if chamber/barrel alignment is not as precise as it would be desirable... Could it compensate such disalignement and exit the muzzle properly oriented and with enough gyro stabilization?

Merçi in advance as always

gatnerd

From: gatnerd

31/10/21

EmericD said:

specs in and of themselves are also a "smokescreen"? It seems that the "135 gr @3000 fps" is what the TV ammo is achieving with a lathe turned copper bullet (as shown in G&A article) or with the 135 gr SMK bullet. That doesn't mean that the XM1186 "GP / EPR" bullet is 135 g @3000 fps, nor than the XM1184 "SP / ADVAP" is 135 gr @3000 fps...

That does open up some interesting possibilities in terms of what 'actual' performance is. 

TV has repped a 135gr projectile, SIG has repped a 135gr projectile, and Cobalt/Mars repped a 140gr projectile. All in the 3000-3200fps. 

But, that could have been based on launching the copper lathe turned 'surrogate' projectile, which as I recall was offered by the gov as a technical drawing for the companies to make for themselves. 

It could be the surrogate projectile is designed not so much to replicate weight, as volume and projectile shape...

At which point we could see the Steel EPR in the 125gr weight class, and the Tungsten AP could be quite a bit heavier ie 155gr + zone. 

Oy, now I feel like we know less then we did a week ago. 

stancrist

From: stancrist

31/10/21

gatnerd said:

It could be the surrogate projectile is designed not so much to replicate weight, as volume and projectile shape...

That doesn't make sense to me. 

For weapon development and function testing, I'd think surrogate ammo would need to have the same bullet weight (and muzzle velocity) as combat ammo.

Plus, the shape of the GP bullet is clearly not the same as that of the machined copper solid (which, IIRC, has only been reported in TV "commercial" loads).

gatnerd

From: gatnerd

31/10/21

stancrist said:

Plus, the shape of the GP bullet is clearly not the same as that of the machined copper solid

Perhaps its more inline with the shape of the Tungsten AP projectile? 

https://imlive.s3.amazonaws.com/Federal%20Government/ID5041233544762060809463086928281536454/NGSW_Industry_Questions_&_Comments_152_-_281_Part_2.pdf

Then theres this:

https://soldiersystems.net/2018/10/04/161298/

* General Purpose (GP) per Drawing titled “6.8MM GENERAL PURPOSE (GP)”. The GP cartridge provides all-purpose solutions for combat, limited training, and basic qualification.
* Surrogate per Drawing 13072652. The surrogate cartridge is designed to mimic the behavior of combat projectiles from a weapon design standpoint. Surrogate projectiles may not be completely representative of the final combat ammunition configuration which are expected to vary during development. Surrogates are intended to be a close replacement shape of the final combat rounds.

This seems to suggest Surrogate is different then the GP projectile in weight and or shape.

Which leaves open the chance that AP load is fairly different in weight and shape then the GP EPR, as if they were more or less the same there would be no need for both to be tested. 

  • Edited 31 October 2021 3:47  by  gatnerd
stancrist

From: stancrist

31/10/21

gatnerd said:

* Surrogate per Drawing 13072652. ... Surrogates are intended to be a close replacement shape of the final combat rounds.

This seems to suggest Surrogate is different then the GP projectile in weight and or shape.

Concur re shape.  The "Industry Questions & Comments" explicitly states that the GP and SP projectiles are different in shape.

However, I do not see anything in the items you quoted which indicates that the GP and SP bullets necessarily differ in weight.

  • Edited 31 October 2021 23:47  by  stancrist
gatnerd

From: gatnerd

1/11/21

SIG NGSW 6.8mm Expert Interview

Full interview with Jason St. John the SIG expert on the MG68 Next Generation Squad Weapon. This future machine gun with replace the US Army's 5.56mm M249 Sq...

Notes:

-SIG has a GPMG version with QCB and handle to allow barrel changes like 240 in the field

-8:50 shows good cutaway of how recoil buffer works

-Claim case can go 2x the pressure of brass, only ~10% of its extra capability used (ability to grow in power for future needs)

-Suggest weapon could also handle even higher pressures without needing big changes

-6.8lmg backwards compatible with 6.5C and 7.62x51 with just a barrel change

-Equal or less recoil to M249 SAW

....

The ability to grow in power within the current cartridge is very interesting, and does speak to the SIG cases advantage over the TV case. 

....

TV is 'moderate' (below 80k) pressure + longer barrel; sensible today but leaves limited room for growth in performance in coming decades. 

...

SIG 80kpsi + short barrel leaves option of say, defeating future Level V armor by going with a longer barrel to increase velocity, and 'Level VI' armor by going Long Barrel + Higher (100kpsi +) in the future. Of course thats predicated on a similarly linear development in armor tech. 

But so far this was my favorite video on SIG's NGSW because it got more into the smaller details that we'd be interested in. 

  • Edited 01 November 2021 5:52  by  gatnerd
smg762

From: smg762

1/11/21

Am i right in thinking that polymer case requires thicker walls, and combining it with 80k PSI would need even thicker walls?

If one had a polymer 80k 5.7x28, would it be substantially larger than the original 5.7?

Mr. T (MrT4)

From: Mr. T (MrT4)

1/11/21

SIG composite case is steel reinforced only on the very bottom,they can apply the same reinforcement to the plastic case from TVC from what i understand about high pressure cases its about supporting the unsuported/unencased part between chamber end and boltface hence the steel case heads. Of course, then there is the question of how well the plastics can hold/ seal the steel case head.

EmericD

From: EmericD

1/11/21

Mr. T (MrT4) said:

SIG composite case is steel reinforced only on the very bottom,they can apply the same reinforcement to the plastic case from TVC from what i understand about high pressure cases its about supporting the unsuported/unencased part between chamber end and boltface hence the steel case heads. Of course, then there is the question of how well the plastics can hold/ seal the steel case head.

True Velocity Composite case proposed for the NGSW program was able to withstand bore obstruction overpressure without any damage.

roguetechie

From: roguetechie

1/11/21

I think sig is talking bigger than they can back up.

Especially about what TV can or cannot do.

And being incredibly blunt, sig NEEDS to do this because their ammo concept is by far the worst, most expensive, and will create the most logistical issues due to the loss of round count per standard pallet!

The best option right now is probably TV ammo in sig guns or Textron.

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