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; 206109 views.
Guardsman26

From: Guardsman26

7-Jul

Exactly. The seal is made as the polymer expands. I believe the pressure of of cartridge ignition forces the polymer to expand outwards, then as the pressure drops, the polymer retracts to its natural position. This means that the front of the cartridge is not cut off causing a circular piece to foul the chamber as it rotates or drops. 

poliorcetes

From: poliorcetes

7-Jul

But that would imply that such precise polymer formula would be enough pressure elastic and not only plastic. I tend to link polymers with plasticity and not with elasticity... but I am not an engineer of any sort, at all.

QuintusO any comments about this? In some folder of my decaying memory it is recorded that you work in a related field

stancrist

From: stancrist

8-Jul

I came across an old video showing the Textron NGSW-R magazine as a double-column, single-feed design.

     https://youtu.be/iSC9wT6m4HA?t=574

Is this rendition accurate?  If so, the Textron magazines must be a royal pain in the arse to fill with cartridges.

Msg 7519.1002 deleted
Guardsman26

From: Guardsman26

9-Jul

Yes. I had noticed that too. 
Separately, an interview with one of the Program officers, Major Wyatt Ottmar, revealed that the US Army is looking at a reduced power NGSW round, so the AP loading that’s causing so much controversy may only be a specialist one rather than a GP round. It’s not clear whether all loadings will use the same (140 grain?) EPR-style projectile. Or whether the projectile will be modified or lightened. 
To be honest, I have reservations about NGSW. It seems like 1950 and the T65 cartridge all over again. We just need the USAF to adopt 6 mm ARC and all will be well! 
 

PRM2

From: PRM2

9-Jul

The Forgotten Weapons video on the Steyr ACR candidate, https://www.forgottenweapons.com/steyr-acr-a-polymer-flechette-firing-bullpup-from-the-90s/ , also mentioned having a single feed magazine, possibly this is a feature of having to reliably deal with 'push feed' polymer cylindrical CT cartridges using a moving chamber.

I wonder if the Steyr ACR also used momentary expansion to form a seal with a moving chamber; hopefully modern materials and development will avoid the muzzle velocity inconsistency that seemed to cause accuracy issues with the Steyr ACR.

ps. original reply deleted to stay on subject - speculation on adapting Steyr ACR design from ring primer to use NGSW CT ammunition deleted.

stancrist

From: stancrist

9-Jul

Guardsman26 said:

Yes. I had noticed that too.

Separately, an interview with one of the Program officers, Major Wyatt Ottmar, revealed that the US Army is looking at a reduced power NGSW round, so the AP loading that’s causing so much controversy may only be a specialist one rather than a GP round. It’s not clear whether all loadings will use the same (140 grain?) EPR-style projectile. Or whether the projectile will be modified or lightened.

That's interesting.  Would the weapons have to be modified to cycle with the reduced-power load?

Guardsman26 said:

To be honest, I have reservations about NGSW. It seems like 1950 and the T65 cartridge all over again.

Indeed it do.  However, the performance with that sleek 6.8mm bullet would answer the calls of many on this forum for a better GPMG cartridge than the T65.

Guardsman26 said:

We just need the USAF to adopt 6 mm ARC and all will be well!

Color me skeptical.  The reported feeding reliability of 6mm ARC magazines seems too poor for combat use, and it hasn't yet been demonstrated that 6mm ARC will even work in belt-fed machine guns.

QuintusO

From: QuintusO

9-Jul

The polymers they're using (PPSU or similar) should be able to handle that just fine. They're very high performance stuff, not really very similar to your everyday ABSes and nylons. Sort of like comparing electroslag refined steel to tin. Both considered metals (or, plastics), but very different stuff.

When I spoke with Kori years ago, she really had no reason to be dishonest (nor do I think she has a penchant for it), and she believed that the obturation problem was well solved. So I think we're seeing backpressure, which is to be expected as especially with a can pressures can remain well in the 4 digits for quite some time after the case has been removed from the chamber of a conventional gun.

Honestly, I had substantial reservations when I saw the first prototypes of that CT carbine, but they seem to have really refined the design. I'm impressed. Everyone here already knows how I feel about the ammunition configuration, so setting that aside, I will say that Textron looks to be clearly in the lead and that at the end of the day we just might get a good (and actually revolutionary!) weapon out of this.

QuintusO

From: QuintusO

9-Jul

There's not a current brass cased cartridge that I'd recommend for adoption right now. And, as I've said a few times, I don't think it's worth considering any round for adoption that has less than 3,000 ft/s (or 900 m/s) muzzle velocity from the standard rifle (there may be exceptions but they're very unusual and they still don't have velocities below 2,700 ft/s). 6mm ARC is well below this (plus, it's designed for lead-cored bullets, so you have to reengineer the whole thing anyway if you want to fling EPRs or copper slugs).

Having said that, I've gone back and forth and up and down what sort of thing it would make sense to adopt, not tooting my own horn but I've probably done more work on this than anybody else here except maybe Emeric, and I am not sure I'm much wiser on this subject than I was a few years ago. If 6mm ARC makes you feel all tingly though, then you might be happy to hear that very capable equivalents can be created with an even more attractive feature set, using technologies developed through NGSW.

stancrist

From: stancrist

9-Jul

PRM2 said:

The Forgotten Weapons video on the Steyr ACR candidate...also mentioned having a single feed magazine, possibly this is a feature of having to reliably deal with 'push feed' polymer cylindrical CT cartridges using a moving chamber.

Not exactly.  The chamber is not moving when the round is being chambered.  But I think you're on the right track.

There is no feed ramp in the Textron rifle, so the flat-faced CT cartridge must be directly aligned with the chamber.

Conventional rounds can be offset from the chamber centerline, but be guided into the chamber by the projectile.

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