https://www.youtube.com/watch?v=hO4IKxECNzI

InrangeTV's MCX Spear disassembly + Thoughts + Live fire

stancrist said:

       Guardsman26 said: My understanding is that SOCOM units deploying with 6.5 and 6 mm weapons have an EPR loading. 

Very interesting.  A pity we can't get a photo of either EPR bullet.

It looks like we got a photo of the 6.5mm EPR.  https://forums.delphiforums.com/autogun/messages?msg=7519.2783

Thanks Emeric!

Guardsman26 said:

I am going to contact you separately to discuss NGSW!!!

Well, that's rude.  The rest of us are interested, too.  

gatnerd said:

Great picture!

Indeed.  So I guess now we know that the 6.5 EPR being used by SOCOM is 103 grains?

stancrist said:

Indeed.  So I guess now we know that the 6.5 EPR being used by SOCOM is 103 grains

I suppose so? 

Previously in this thread, a member here kindly analyzed the 6.8 EPR and figured the projectile weight had to be ~120gr, not the 135gr we had assumed. And thats with a nice long projectile.

So then it would stand to reason that a 6.5 EPR based on a comparably nice form factor would be lighter then the 6.8. A reduction of 17gr weight seems reasonable given the reduction in diameter and (probably) length. 

Notably Nathanials 6.8 and 6.5 EPR design - also a very fine shape - ended up with a 125gr 6.8 and 108gr 6.5 when using the same form factor. 

https://www.thefirearmblog.com/blog/2017/09/09/romulan-vulcan-preference-driven-vs-process-driven-design-field-small-arms-ammunition/

So further to your comments, I understand that the 6.5 mm Creedmoor with a 6-7 gram EPR bullet is fired at a higher chamber pressure (70,000 psi). This enables it to use standard brass (making a polymer case version potentially possible).. I further understand that the overall configuration delivers comparable penetration to 6.8x51 mm out of 14/16” barrels. (Anecdotally I am hearing Level IV defeat, but to 400 metres instead of 500 metres - SIG doesn’t quite do it at 600 metres, especially with shorter barrels). 
 

So with high pressure 6.5x48 mm Creedmoor SP you are delivering overmatch in a lighter package (18-19 grams versus 21-22 grams) with a cartridge that is also much easier and less expensive to produce. Because it runs less hot with lower pressures, barrel and parts wear should also be reduced. 
 

If it works as I think it does, it may be a much better overall solution than 6.8x51 mm. Indeed 6.5x48 Creedmoor SP could yet become the NGSW standard. 

6.5 Creedmoor is a 62kpsi cartridge, and 6.8 NGSW is much faster out of 14-16” barrels due to being a 75-80kpsi cartridge.

The 6.5 Creedmoor case has less taper and a sharper shoulder than the 7.62x51 and 260 Rem.  Have these presented any problems in weapons function?

gatnerd said:

6.5 Creedmoor is a 62kpsi cartridge, and 6.8 NGSW is much faster out of 14-16” barrels due to being a 75-80kpsi cartridge.

The commercially available 6.5x48 mm Creedmoor cartridge shoots at 62,000 psi. But insiders tell me that the military version developed by SOCOM and incorporating an EPR bullet, shoots at 65,000-70,000 psi. The 6.5 mm bullet mass is 105 grains (6-7 grams) versus 120 grains (8-9 grams) for 6.8x51 NGSM. So performance should be almost as good. 

I am going to suggest that 6.5x48 mm Creedmoor SP penetrates Level IV plate at 300 metres, while SIG's 6.8 mm cartridge does so at 500 metres. If the 6.5x48 mm Creedmoor can deliver this level of performance using standard brass in a cartridge with a lower weight, and less recoil, it will offer a better set of compromises that could weigh in its favour. At the very least, I expect the excellent work being done by SOCOM to influence the final NGSW standard. 

Also, SOCOM is also fielding a weapon in 6x39 mm ARC, also with an EPR bullet. If you extend the ARC case to 45 mm and put more powder behind it, it may be possible to deliver respectable Level IV penetration in a cartridge close in weight to 5.56 mm but that overmatches 7.62 mm beyond 300 metres.  

@nincomp

No issues with belted 6.5 mm CM.

Guardsman26 said:

I expect the excellent work being done by SOCOM to influence the final NGSW standard. 

In what way(s)?

Guardsman26 said:

Also, SOCOM is also fielding a weapon in 6x39 mm ARC, also with an EPR bullet. If you extend the ARC case to 45 mm and put more powder behind it, it may be possible to deliver respectable Level IV penetration in a cartridge close in weight to 5.56 mm...

A 6x45 ARC would weigh ~16 grams.  That is a little closer to 5.56x45 NATO than 6.5x48 CM at 18 grams, but not by very much.

And unless completely new NGSW-R and NGSW-AR of reduced size would be developed, I'm doubtful it would be worth doing.