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NGSW Phase 2 Consolidation and info   Small Arms <20mm

Started 30/8/19 by gatnerd; 453293 views.
smg762

From: smg762

21/9/21

Not to derail the topic, but has there been much development of coilguns/gauss guns.

-in terms of magnetically holding the bullet in place. And then getting some 'assistance' from the cartridge, removing the need for a big power source?

gatnerd

From: gatnerd

21/9/21

stancrist said:

Reliability of feeding, chambering, extraction with such an extreme L:D, and zero case taper?

Hard to say; 5.7x28 employs a similarly 'taperless' design, albeit shorter. Reliability is quite good, but coatings on the 5.7 brass may be a factor. 

A modification of the concept is certainly possible, where the case is made slightly wider in the rear and tapers forward. For example say something equivalent to .25 ACP at the base (0.278") tapering to 0.253" (neck diameter of current 5.56x45). 

Basically the design goals would be for a cartridge that allows:

- a 50rd double stack magazine that is ~ 8" long 

-Velocity and energy comparable to 5.56 / 5.45 

Anything after that would be open to the designers. 

gatnerd

From: gatnerd

21/9/21

VPMudde said:

The following is an estimate for the projectile made from images available online

Heres the only pic out there of the 6.8 GP, which may help with your estimates:

gatnerd

From: gatnerd

21/9/21

EmericD said:

But from Buffman video, the bullet seems highly magnetic, and tungsten carbide is not magnetic at all.

In the video, Buffman describes it as mildly magnetic. Various WC alloys are midly magnetic due to use of iron and cobalt in the alloy / binder:

https://blog.carbideprocessors.com/tungsten-carbide/tungsten-carbide-and-magnetism/

This lead me down an interesting rabbit hole of 'is M993 magnetic' which lead to this post:

https://www.migunowners.org/forum/showthread.php?399832-Thoughts-on-armor-piercing-bullets-in-AR-pistols/page2

So that cobalt binder could explain the magnetism, and also explains why both M993 and AP485 were pretty lame penetrators - they tended to shatter on impact. 

But the following paragraph is of extreme interest to the NGSW / AP problem, and could help explain why Buffman's testing is showing such very different results then what the US Army is expecting out of NGSW. It could also explain why your results with the MEN DM151 are so much better then M993. 

The use of a more shatter resistant tungsten formulation would radically change our expectations of what is possible for AP / NGSW. 

More info on Liquid Phase Sintered (LPS) Tungsten Alloy:

https://apps.dtic.mil/sti/citations/ADA474421

https://www.hindawi.com/journals/jpt/2014/764306/

https://www.hindawi.com/journals/jpt/2014/764306/

But overall this suggests there is a good bit of performance beyond what we've seen out of M993/AP485 out there by improvements in tungsten carbide production to make it more shatter resistant. 

And MEN may be using these better techniques then what NAMMO was doing with M993/AP485. 

This company in the US, which makes tungsten parts / fragments for the US military, makes mention of LPS in the production process:

https://tungstenparts.com/tungsten-manufacturing-operations/

Overall it may be the case that a newer, better tungsten AP has arrived and our previous understanding of NGSW's practicality - based on Buffman's testing - may no longer apply to the same extent. 

  • Edited 21 September 2021 17:41  by  gatnerd
VPMudde

From: VPMudde

21/9/21

EmericD said:

The bullet is longer (L/D ~5.15) with a slender nose (~2.84 cal).

A bullet like that is actually even lighter than my estimate, there being more nose cone and less shank. 

@Gatnerd: that is the exact image i got my estimate from. However, when I went to measure it again just now ended up at 5.1 caliber length, 2.67 cal nose cone, and 0.15 cal meplat. Still only gets you to 125.5 grains.

  • Edited 21 September 2021 20:59  by  VPMudde
stancrist

From: stancrist

21/9/21

Perhaps you are using incorrect density?

VPMudde

From: VPMudde

21/9/21

For an EPR 8.5 is about right. That is assuming 40% by weight of steel (7.8), and 60% copper (8.9). I'll give you 8.6 even (30%/70%), for all the 1.5 grains that wins you. For 135 grains you need to go over 9.

What other posibilities are there besides tungsten containing AP and lead FMJ/OTM weighing 135 grains, and the EPR's mass is yet to be disclosed, or the EPR is also 135 grains but isn't lead/tungsten-free.

  • Edited 21 September 2021 22:10  by  VPMudde
gatnerd

From: gatnerd

22/9/21

VPMudde said:

Does that mean that the 135 gr figure is only for the AP variant (due to the use of tungsten)? And that the GP projectile is actually a fair bit lighter than AP? Or am I wrong about this shape? 

There has not been an official spec ever posted; quite the contrary - the specs were originally shrouded in secrecy. Original speculation for the 6.8 HVAP that preceded NGSW was a 6.8 125gr @ 3300-3500fps as the goal.

Then Soldier Systems published SIG's specs for their .277 Furry load / NGSW weapons. Specs were 135gr @ 2850fps from a 13", 3000fps from a 16".

Later, Cobalt / MARS shared their project - a 140gr @ 3200fps.

Most recently, a video of TV's / GD's bullpup mentioned 135gr @ 3000fps from their 20" barrel at 60kpsi. 

So we know that these companies are designing their cartridges around firing a 135-140gr projectile. Probably this is the 'surrogate' projectile mentioned in the initial NGSW program filings. 

So if the 135-140gr is the Surrogate, its entirely possible that the steel + copper EPR 'GP' is indeed lighter, maybe 125gr as your model suggests. 

If it is 125gr, we'd then likely expect velocity to be around 3100fps, based on the 135gr x 3000fps.

If the 6.8 AP uses the same EPR construction of the XM1158, where the steel tip is replaced by Tungsten carbide, but otherwise retains the same size and shape of the 6.8 GP, then we'd obviously see a difference in weight, since WC is ~2x the density of steel.

That would be worth modeling I think - if the steel EPR is ~125gr, whats the weight of the same projectile with the steel swapped for WC?

  • Edited 22 September 2021 2:13  by  gatnerd
stancrist

From: stancrist

22/9/21

gatnerd said:

Cobalt / MARS shared their project - a 140gr @ 3200fps.

Most recently, a video of TV's / GD's bullpup mentioned 135gr @ 3000fps from their 20" barrel at 60kpsi. 

So we know that these companies are designing their cartridges around firing a 135-140gr projectile. Probably this is the 'surrogate' projectile mentioned in the initial NGSW program filings.

It seems rather unlikely there are two government-provided surrogates.

The bullet seen in the Cobalt/MARS round is probably not the surrogate.

The SIG, TV, and Textron rounds have what is likely a 135gr MatchKing.

.270 CALIBER 135 GR. HPBT MATCHKING – Sierra Bullets

EmericD

From: EmericD

22/9/21

VPMudde said:

A bullet like that is actually even lighter than my estimate, there being more nose cone and less shank.

The original EPR design used a bismuth core. Maybe the XM1186 solved the high temperature problem that plagued the 5.56 mm accuracy?

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