gatnerd

Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.

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NGSW Phase 2 Consolidation and info   Small Arms <20mm

Started 30/8/19 by gatnerd; 550535 views.
EmericD

From: EmericD

24/5/22

Apsyda said:

Its that if SIG knew how big the NGSW FC was going to be, they likely would have designed the receiver or feed system differently to account for it. I doubt any SIG engineer is happy with that big bridge rail over top of the action. And should they have known that the NGSW FC was large enough to have its own ZIP Code, they likely would have accounted for that.

I agree that the rail over the feeding cover is far from ideal, but I don't think that it's related to the size of the NGSW FCS, which do not seems to be significantly longer than any commercial 1-8x LPVO.

Apsyda said:

The barrel being easily replaceable doesn't really help much in the field. While our armorer friends in the world can smile about it, everyone using the gun now constantly has to be cognizant of the potentially quite short time to the barrel overheating. At which point there isn't much that can be done about it. Perhaps in the future they'll copy the PKP and put a Lewis radiator system over the barrel. Adding a several lbs to the firearm but giving it more sustained firepower capability.

That's right, but since a rifle like the HK416 could fire 300+ rounds in full auto without overheating, and can fire again the same diet of ammo after 30 minutes of cooling, maybe the lack of "field QC" capability is more a theoretical issue than a real issue?

A 100-rds belt of 6.8x51 mm (with pouch) is ~3.1 kg, so 300 rds is already 9.3 kg of ammo... I don't think that the automatic rifleman will carry more than 4x100 rds (to "duplicate" the 4x200 rds of 5.56 mm currently carried).

stancrist

From: stancrist

24/5/22

EmericD said:

Our capability to draw opposite conclusions from the same set of informations will never ceased to puzzle me.

Well, that is one thing we agree on.  sunglasses

stancrist

From: stancrist

24/5/22

EmericD said:

       Apsyda said: The NGSW-AR is firing a hot magnum cartridge, but doesn't have a QC barrel.

The SIG NGSW-AR does have a QC barrel. Not very ergonomic and not designed to be changed when hot during combat, but a QC barrel.

Partial disassembly of the gun required + removeable-by-user-only-when-cold barrel =/= quick change barrel

stancrist

From: stancrist

24/5/22

EmericD said:

       Apsyda said: Its that if SIG knew how big the NGSW FC was going to be, they likely would have designed the receiver or feed system differently to account for it. I doubt any SIG engineer is happy with that big bridge rail over top of the action. And should they have known that the NGSW FC was large enough to have its own ZIP Code, they likely would have accounted for that.

I agree that the rail over the feeding cover is far from ideal, but I don't think that it's related to the size of the NGSW FCS, which do not seems to be significantly longer than any commercial 1-8x LPVO.

Judging by the graphic at 9:40 in this video ( https://youtu.be/ZrKOLyLUZmI?t=580 ), the problem is a result of poor planning by SIG engineers. 

With the side-opening top cover, an optic must be mounted either completely on the top cover, or fully on the section of rail behind the top cover.

If the NGSW FCS were to be positioned on the weapon with correct eye relief, it looks like the mount would clamp to both the top cover and the rear rail section, making it impossible to open the top cover.

stancrist

From: stancrist

24/5/22

Apsyda said:

The NGSW-AR...had to add a ridiculous bridging top rail because obviously there was little intercompany and intratrial communication as to how large the NGSW-FC optic would be.

The problem was not caused by a communication failure.  The bridging rail was needed because of a design flaw.

SIG had designed the LMG receiver so that only optics of certain dimensions and/or configurations could be used.

They knew a common FC optic would be used for both NGSW-R and -AR, and yet the SIG LMG was always seen fitted with a compact RDS, while the MCX Spear rifle usually had a much bigger LPVO.  Had the LMG been designed from the start to use the LPVO, the bridging rail likely would not have been needed.

Overview of the Sig Sauer MCX Spear and XM250

Guns.com recently got to hang out with the folks from Sig Sauer and learned about the company's successful submission to the Army's Next Generation Squad Wea...

stancrist

From: stancrist

24/5/22

The folks at Battle Order have joined in.  sunglasses

gatnerd

From: gatnerd

25/5/22

Nice, I love their posters. 

gatnerd

From: gatnerd

25/5/22

Watching this interview on SIG's 6.8 ammo:

https://youtu.be/yUVX_Bup0Ig?t=829

-Cases currently running "mid 70's" pressure aka around 75kpsi

-Claim the cases can be run to 120kpsi should the future require it

Apsyda

From: Apsyda

25/5/22

Man, thats worse than what I said.

Gotta love SIG.

Guardsman26

From: Guardsman26

25/5/22

I agree with Emeric. A standard pressure 6.8x51 mm NGSW must be VERY close in performance to 6.5 x 49 mm Creedmoor. I believe SOCOM has its own 6.5 mm EPR-style projectile that is identical to the 6.8 mm NGSW projectile in terms of profile, but weighs less - 6-7 grams. A 6.5x49 mm CM fired at standard pressure (55,000-60,000 psi) has the advantage of weighing 18-19 grams versus SIG's 6.8x51 mm cartridge at 21-22 grams. You can also use the 6.5 CM lower chamber pressure to engineer a polymer case to deliver a lower weight cartridge, close to 16 grams. 

Emeric, I am not a ballistician, but what do you estimate would be the chamber pressure of a 6-7 gram 6.5 mm bullet fired from a 6.5x49 mm Creedmoor cartridge at 3,000 fps / 914 mps? 

Second pint, popped primers with FN SCAR are due to some manufacturers using soft metal primers, not military spec ones. SCAR is designed to meet very demanding military standards. It is designed to achieve 1 mm of penetration for military spec 7.62 mm and 5.56 mm cartridge primers. With soft primers it is achieving 1.5 mm or 2 mm. The latter is obviously too much. I know this, because I was on the range with FN today, and asked their technical lead. (I was firing Evolys in5.56 mm and 7.62 mm ). 

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