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U.s. Army Next Generation Squad Automatic Rifle

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#41 lastdingo

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Posted 08 June 2017 - 1205 PM

One could have used 7x57 mm Mauser throughout the last 124 years and would not have been served much worse than by the dozens of different major military cartridge patterns used instead.

 

 

BTW, I noted that the requirement includes an "Intelligent rail" with data transfer function:
 

APA 13 Data Transfer (Intelligent Rail)

 

Does this mean STANAG 4694 NATO accessory rail is already obsolete, and the intended power transfer version of it is obsolete as well?

Now it has to be a downwards compatible rail with electrical power transfer and data transfer?



#42 T-44

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Posted 08 June 2017 - 1216 PM

(...)
In both of these cases, the old cartridge was only a little off, and its successor significantly overcompensated.


Maybe in part because a "more ideal" successor would otherwise have only offered a perceived too limited advantage to justify the switch.

#43 seahawk

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Posted 08 June 2017 - 1227 PM

Maybe the answer is to accept that there is no ideal one size fits all solution. The PKM is so much talked about because Russia decided to keep the calibre even when going to another (more than once) with the assault rifles.



#44 17thfabn

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Posted 08 June 2017 - 1229 PM

Wasn't there a U.S. Army R&D program to build a SAW type weapon of 6mm caliber back in the 70's?



#45 TTK Ciar

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Posted 08 June 2017 - 1450 PM

Maybe the answer is to accept that there is no ideal one size fits all solution. The PKM is so much talked about because Russia decided to keep the calibre even when going to another (more than once) with the assault rifles.


The problem I fall into is that interpreting the effects of ballistic improvements is dependent on political factors.

A modestly heavier bullet (85 grains is about the sweet spot) with a good shape and modestly more energy than 5.56x45 leaves the barrel a bit slower, but retains much more of its velocity downrange and is less subject to wind drift and the like.

But how to measure the effect of this? It should be easier to hit the target with such a thing -- if infantry is trained to shoot effectively at such ranges. How likely is that? The composition of the bullet will also influence the inflection points of lethality vs velocity. American-made M855 fragments well at 2600 ft/s or higher, but bullets can be designed to fragment well at velocities as low as 1900 ft/s, but again how likely is that? The M885A1 is significantly less prone to fragmentation, and the UK MoD is entirely intolerant of bullets that fragment at all.

So, looking at the velocity-vs-range chart, what's the lethality inflection point? 2600 ft/s? 1900 ft/s? Or do we pretend soldiers will be doping their bullets with bark scorpion venom, decoupling terminal effects from velocity and mass altogether? Or will soldiers be shackled with bullets that just poke a pencil-hole?

It's a rabbit-hole of similar depth and twist as the "why not simply give soldiers indirect fire support?" question.

#46 17thfabn

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Posted 08 June 2017 - 1550 PM

Wasn't there a U.S. Army R&D program to build a SAW type weapon of 6mm caliber back in the 70's?



#47 Rick

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Posted 08 June 2017 - 1609 PM

Does it seem to anyone else like each change in US military cartridge overcompensates for the lessons learned from its predecessor?

30-06 was a good machine gun cartridge, but a bit too long and powerful for an infantry rifle cartridge. This led to the development of 7.62x51, which is a bit underpowered and too short for bullets to have both good weight and a long, narrow ogive shape.

5.56x45 was an early stab at the US developing an assault rifle cartridge, and it has proven a little too light for the role. This led to the development of .264 USA, which is a little too heavy (302 grain with brass case and 108 grain bullet) for infantry to carry a full load, and too wide for bullets of a desirable weight to have a good ballistic coefficient.

In both of these cases, the old cartridge was only a little off, and its successor significantly overcompensated.

Can't remember the calibers, but the German WW2 Kurtz (spelling?) round or the AK47 round?



#48 lastdingo

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Posted 08 June 2017 - 1615 PM

"kurz" (= "short") spelling

Both 7.92x33 and 7.62x39 suffered from being too slow for easy and accurate aiming against small targets at ~300 or laterally moving targets. Personally I think 800 m/s  - 900 m/s is a sweet spot.

-------------

@17thfabn

Yes, but U.S. Army R&D programs for small arms very rarely yield any all-new designs in service. The introduction of the AR-15 pattern into service came through the air force, McNamara and political luck. The army R&D was toying with very different concepts https://en.wikipedia...dividual_Weapon

 

It's actually best to simply ignore all U.S.-Army small arms R&D programs ... I mean, nobody's caring about XM-8 anymore right? It was all wasted attention.

Admittedly, I wasted attention here as well, though my real intention here was of course to bring across a few points on infantry tactics.



#49 bojan

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Posted 08 June 2017 - 1706 PM

5.56 is quite OK for rifles/carbines, as is 5.45 and 5.8.

All are iffy for LMGs.



#50 shep854

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Posted 08 June 2017 - 1814 PM

Pity Anthony Evans drifted away.  This is right up his alley; he had good ideas about a medium-caliber cartridge.



#51 lastdingo

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Posted 08 June 2017 - 1817 PM

double post

Edited by lastdingo, 08 June 2017 - 1828 PM.


#52 lastdingo

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Posted 08 June 2017 - 1827 PM

5.56 is quite OK for rifles/carbines, as is 5.45 and 5.8.
All are iffy for LMGs.


LMGs need be controllable on bipod out to about 300 m for suppression of window positions etc, so those low impulse cartridges make some sense for LMGs.

My question is why you think that the demands on the external or terminal ballistics of a LMG are or should be different than for rifles/carbines?

Pity Anthony Evans drifted away. This is right up his alley; he had good ideas about a medium-caliber cartridge.


Lots of people did so, particularly intermediate cartridges above 5.56 were fashionable ideas for a long time (especially 2004-2010 or so).
I myself argued in favour of a medium cartridge between 5.56 and 7.62 for dismounted forces and an intermediate cartridge between 7.62long and 12.7 for mounted forces / vehicles.
The ~7mm cartridge would address the terminal ballistics concerns about 5.56 and the ~.338 cartridge would defeat all those plating that was meant by design to resist 7.62, but not 12.7 (~STANAG 4569 level 3) and be generally more useful through brick walls.

Nowadays I'm more focused on getting the weight for infantry and scouts down, so I'm fine with the current puny cartridges for carbines and LMGs.

(The first time I saw a 5.56 mm cartridge sometime in the mid-90's after being trained on G3 / MG 3 I thought it was a cartridge for the FN P90 - it looked so tiny!)

#53 bojan

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Posted 08 June 2017 - 1902 PM

LMGs need be controllable on bipod out to about 300 m for suppression of window positions etc, so those low impulse cartridges make some sense for LMGs.

FFS, I have fired M84 (PKM) quite accurately up the 500m after about month and half of training (which was not just machinegun training). And that was w/o optics. With 4x optics 800m was reasonably possible. If you need 5.56 to fire LMG accurately at 300m you are not good enough to be ever issued one.

 

 

My question is why you think that the demands on the external or terminal ballistics of a LMG are or should be different than for rifles/carbines?

To engage targets that are out of the effective range of rifles/carbines and for better barrier penetration.

Instead of burdening every infantrymen with 7.62x51mm rifle (like it seems US wants to do again) give LMG ~0.65kg (that is all the difference between empty PKM and Minimi!). Give a squad 7.62x51 DMR.

Squad is made of 2 teams, one assault with as many riflemen as possible, other FS with LMG, DMR and possibly grenadier. If you want to go fancy make 5.56mm mag fed SAW (20" heavy barrel, bipod) that can follow assault element, but it is not that needed.

Or make some magic "universal" caliber that will not cripple LMG and DMR, but good luck convincing army to adopt it.



#54 Simon Tan

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Posted 08 June 2017 - 2104 PM

The first failure to understand the PK is that the old rimmed cartridge is indeed a blessing, though for unobvious reasons. It precludes a push through link and thus by default you require a pull out link. This means the act of stripping a cartridge from the belt is carried out during the high energy recoil stroke and not the return stroke. This has the additional benefit of bleeding energy from the recoiling mass, reducing the impulse on the rear trunnion. The return stroke chambers the loose round, which is a lot easier than stripping and chambering per push through. Yes, there can be disintegrating pull out links for rimless cartridges. They have them for Brownings.

 

*sigh*



#55 rohala

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Posted 08 June 2017 - 2110 PM

LMGs need be controllable on bipod out to about 300 m for suppression of window positions etc, so those low impulse cartridges make some sense for LMGs.

FFS, I have fired M84 (PKM) quite accurately up the 500m after about month and half of training (which was not just machinegun training). And that was w/o optics. With 4x optics 800m was reasonably possible. If you need 5.56 to fire LMG accurately at 300m you are not good enough to be ever issued one.

You probably fired single shots. My understanding is also that firing full-auto a full power caliber LMG from a bipod beyond 300 meters is futile.
In any case, I remember a couple years ago looking at US marksmanship standards, and I remember that clearly more accuracy was expected from the M249 than the M240 (EDIT to clarify: firing bursts).

Edited by rohala, 08 June 2017 - 2113 PM.


#56 Simon Tan

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Posted 08 June 2017 - 2123 PM

PKM doesn't fire in semi.



#57 sunday

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Posted 09 June 2017 - 0319 AM

The first failure to understand the PK is that the old rimmed cartridge is indeed a blessing, though for unobvious reasons. It precludes a push through link and thus by default you require a pull out link. This means the act of stripping a cartridge from the belt is carried out during the high energy recoil stroke and not the return stroke. This has the additional benefit of bleeding energy from the recoiling mass, reducing the impulse on the rear trunnion. The return stroke chambers the loose round, which is a lot easier than stripping and chambering per push through. Yes, there can be disintegrating pull out links for rimless cartridges. They have them for Brownings.

 

*sigh*

 

Also, rimmed cartridges, and pull out belts, make it easy to shorten the receiver, reducing weight. First time I saw a PKT I was amazed to see how small and short the thing is.


Edited by sunday, 09 June 2017 - 0319 AM.


#58 Panzermann

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Posted 09 June 2017 - 0523 AM

The first failure to understand the PK is that the old rimmed cartridge is indeed a blessing, though for unobvious reasons. It precludes a push through link and thus by default you require a pull out link. This means the act of stripping a cartridge from the belt is carried out during the high energy recoil stroke and not the return stroke. This has the additional benefit of bleeding energy from the recoiling mass, reducing the impulse on the rear trunnion. The return stroke chambers the loose round, which is a lot easier than stripping and chambering per push through. Yes, there can be disintegrating pull out links for rimless cartridges. They have them for Brownings.
 
*sigh*

 
Also, rimmed cartridges, and pull out belts, make it easy to shorten the receiver, reducing weight. First time I saw a PKT I was amazed to see how small and short the thing is.


Because the belt and feed mechanismn is stacked above the chamber and not behind the chamber as in most other machine guns. Thus shortening the overall length.

#59 sunday

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Posted 09 June 2017 - 0529 AM

Exactly.



#60 rohala

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Posted 09 June 2017 - 0545 AM

PKM doesn't fire in semi.

Machinegunners are trained to control the trigger so as to be able, ideally, to fire single shots.




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