I don't recall if this has previously been covered, but news to me is that 6.8x51 case construction has been simplified; the original 3-piece case was succeeded by a 2-piece design.

SIG SAUER Supports SOF Weapon Needs | Defense Media Network

Also, 6.8x51 cartridges produced for the Army have darkened case heads.  Empty case weight = 10 grams.  

https://forum.cartridgecollectors.org/t/actual-sig-sauer-6-8x51mm-next-generation-squad-weapon-composite-cartridge-case/52615

And a nice pic of a 6.8x51 loaded round with GP bullet, in case anyone would like to crop it.  

Are those two rounds to scale?

When i was making my rifle magwell i bought all sorts of mags and  6.5Grendel ,6.8SPC , 6ARC was just and engraving on same magazine no alteration whatsoever, the body of the mag is actually designed for 6.8SPC .

autogun said:

Are those two rounds to scale?

stancrist said:

Also, 6.8x51 cartridges produced for the Army have darkened case heads.  Empty case weight = 10 grams

Superb find Stan.

Estimated 6.8 weight:

Hybrid Case: 155gr 

Large Rifle Primer: 5gr

EPR Estimate*: 135gr

Powder Estimate*: 51gr

= 346gr / 22.42 grams per 6.8x51 cartridge 

Biggest variable is what the actual GP projectile weighs, could be lighter.

But it's clear we're dealing with a cartridge very marginally lighter then 7.62x51. The 'lightweight case' is really not that light at all. 

Cropped image high rez:

https://i.ibb.co/59FPQsW/6-8x51-NGSW-EPR.png

And reasonable forum size

When two rounds of the same purpose (i.e. infantry rifles and LMGs) are shown side by side, apparently in a comparison photo, there is a normal assumption that they will be to scale. 

gat i had 2 questions.

what's the approx. weight of a polymer cased 7.62x51 or 6.8?

did textron's CT round use a plastic case and was it lighter than the others?

assuming a full power muzzle energy, what ME would the 6.8 have at 350meters or so?

random question. what was the weight of GD's rifle? i think i read it was 3.3kg with suppressor, which seems awfully light.

also, if you had a NGSW rifle where the barrel recoiled a long way, like 4 inches, would it reduce recoil more than GDs offering?

smg762 said:

random question. what was the weight of GD's rifle?

Specific answer to your random question:  I don't know.

autogun said:

When two rounds of the same purpose (i.e. infantry rifles and LMGs) are shown side by side, apparently in a comparison photo, there is a normal assumption that they will be to scale.

Tony, I took your question to be in jest.  But if you genuinely do not know whether those two rounds are to the same scale, then I strongly urge you to go immediately to the nearest hospital emergency room.

At my last job, one day I noticed a co-worker was confused about a rather simple, routine matter.  I thought something was wrong with him, but I said nothing.  Two days later he died from the untreated stroke.