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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; 204522 views.
EmericD

From: EmericD

25-Jun

poliorcetes said:

But how such hotter gas would decrease barrel life even more than a, say, bullet travelling down the bore at 1150 m/s?

It is an accepted fact that barrel throat erosion is directly linked to flame temperature, hence an indirect effect of chamber pressure.

If you want to include bullet MV in the global picture, you need also to take into account that the M193 achieved 990 m/s in a 20" barrel, with a bullet with a SD of 0.156. The SD of the 6.8 mm bullet is 0.251, so that's equivalent of a 88 gr 5.56 mm bullet.

Now, just imagine that someone ask you to design a 5.56 mm cartridge able to launch a 88 gr bullet with a MV of 915 m/s from a 13" barrel. Do you think that this round will have something in common with the .223 Remington, or will it be closer to the .220 Swift, or even more "overbore"? 

EmericD

From: EmericD

25-Jun

We have already discussed this issue, but I think that:

- from a training & logistic point, we need the same platform for the role of the PDW and the role of the IW,

- from an ergonomic point of view, a future common cartridge should be build around the "micro action" of the 5.56 mm / 5.45 mm / 7.62x39 mm,

- the same constraint imply that you will probably have a 25 rounds magazine with a .30 Remington or 7.62x39 mm casehead, and 20 rounds with a 12 mm casehead,

- from a cartridge design point, a 6.5 mm VLD bullet will eat a lot of volume, so we need probably to aim at .224", .236" or .243" bullet diameter.

Having said that, I think that the current 6 mm ARC with a 95 gr lead-free bullet is probably all you need for covering most your combat need, add a .338 Norma sniper rifle and MMG at a higher organizational level to cover all the direct-fire missions.

Guardsman26

From: Guardsman26

25-Jun

I agree. 

A 6 mm EPR-style low-drag projectile in a cartridge based on a .30 Remington / 7.62 x 39 mm casehead (11.1 mm) seems the best compromise. However, a 12 mm casehead may allow sufficient extra energy needed to achieve some measure of range body armour defeat. 

I'm trying to remember what you said about bullet weights to achieve a suppressive effect. Is 95 grains enough?

Could a future pistol / PDW standard emerging around FN's 5.7 mm cartridge? This seems to have gained market acceptance above H&K's 4.6 mm offering. A PDW / SMG weapon could equip AFV and helicopter crews, vehicle drivers, and artillery personnel. It wouldn't need to be effective beyond 200-300 metres. 

Ultimately, 5.7 mm 6 mm and 8.6 mm would be a good mix of calibres.  

EmericD

From: EmericD

25-Jun

Well, a 12 mm case head (6 mm BR) could allows for more case volume if you are planning to use free-flowing powder with apparent density below 1, but with a compressed powder load and a binder, you could achieve an apparent density around 1.5 so smaller cases will provide more than enough case volume if you choose to follow this path.

For a 6 mm bullet, an impact energy around 700 J should gives you the equivalent suppressive effect of a 7.62 mm NATO impacting just above Mach 1 (750-800 m), not too difficult to duplicate with a 95 gr bullet up to more than 600 m.

njb3737

From: njb3737

25-Jun

Our , to the best of your knowledge  any European Armies evaluating calibres other then 5.56 & 7.62 for mainstream use ?

   

EmericD

From: EmericD

25-Jun

The European Defense Agency is launching a 4 years program called "SAAT", to study and propose a "new generation" of ammo (and associated weapons).

Our SF community is buying some weapons in 6 mm ARC for operational evaluation.

njb3737

From: njb3737

25-Jun

Thank you , a great opportunity to get this right. 
 

stancrist

From: stancrist

25-Jun

EmericD said:

I think that: - from a training & logistic point, we need the same platform for the role of the PDW and the role of the IW,

I must disagree.  I see no reason to think using the same platform for PDW and IW is a need.

And for those military jobs that really require a PDW, the IW is simply too big, if not too heavy.

EmericD

From: EmericD

25-Jun

Yes, in the past it was different and there was also the M1 SMG for providing full-auto fire at short range. Fortunately, we learned a few things since the 40-50's.

Do you think there is a need in 2020's to issue 2 different platforms firing 2 different ammo, when you can issue only one platform and a common ammo? Because that's exactly the point of NGSW, to provide one platform (well, 2) and 6.8 mm ammo for the infantry branch, and the M4 firing the 5.56 mm for the PDW role.

So instead of a general issued weapon, the NGSW is a specialist weapon. I can see the rationale behind this idea, I simply don't think that's a good idea when you can issue something like a 6 mm ARC for everyone, which will not be bigger than a current 5.56 mm weapon.

Isn't the pilot pictured above issued a GAU-5A in 5.56 mm?

stancrist

From: stancrist

25-Jun

EmericD said:

Do you think there is a need in 2020's to issue 2 different platforms firing 2 different ammo, when you can issue only one platform and a common ammo?

Therein lies the disagreement.  I doubt that we can issue only one platform and just one caliber.

For one thing, to have only one platform, you have to go either 100% mag-fed, or 100% belt-fed.

Neither seems a realistic option.  Plus, how do you expect someone like this guy to carry a rifle?

https://youtu.be/HyrAqNv1odM?t=207

EmericD said:

Because that's exactly the point of NGSW, to provide one platform (well, 2) and 6.8 mm ammo for the infantry branch, and the M4 firing the 5.56 mm for the PDW role.

Not exactly.

First, if the Textron or SIG candidates are adopted, there will be two NGSW platforms, not one.

Second, I am pretty sure 6.8mm weapons will not be issued to everyone in the Infantry branch.

I expect that clerks, cooks, mechanics, etc, in infantry units will be armed with the 5.56mm M4.

Which means that infantry units will have three platforms and two calibers.  Much like in WWII.

Correction:  Better make that four platforms and three calibers.  I forgot to include 9mm pistols.

EmericD said:

So instead of a general issued weapon, the NGSW is a specialist weapon. I can see the rationale behind this idea, I simply don't think that's a good idea when you can issue something like a 6 mm ARC for everyone, which will not be bigger than a current 5.56 mm weapon.

I'm a little skeptical of 6mm ARC, but I do like your basic idea for replacing 5.56mm with a 6mm round.

I just think it is not feasible to have one platform for everyone.  I gave some reasons, here is another:

The Army recently adopted a new 9mm SMG, because the M4 is too big for the mission requirements.

Switching to 6mm for carbines would not eliminate the requirement for those 9mm submachine guns.

EmericD said:

Isn't the pilot pictured above issued a GAU-5A in 5.56 mm?

Probably not.  That pilot is in the Canadian air force.  AFAIK, only the US Air Force issues the GAU-5A rifle.

I don't know if US Navy or Marines issue anything other than pistols.  070819-M-0000A-000 (marines.mil)

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