mpopenker said:

and IIRC the standard barrel steel there is the equivalent of the German 41CrMo4 steel

This steel is nothing special at all. Its a pretty common steel for tools and general mechanical construction. Quality bicycle parts are often made from it for example.

schnuersi said:

This steel is nothing special at all. Its a pretty common steel for tools and general mechanical construction

And who said it was something special?

Sorry, do not know the AUG barrel steel. All I know is that the StG77 barrels were cold forged on GFM machines, just like HK barrels were.   

mpopenker said:

And who said it was something special?

Nobody.
I am just wondering what the problem is if an industrial standart solution delivers the results you mentioned. To me it seems like a really effective approach cost to performance wise.

Came across this interesting slide on Twitter, showing SIG's hybrid 7.62 as an AP round:

https://twitter.com/2805662/status/1628607690430902272/photo/1

Notable aspects of the slide:

1. +500fps claimed (vs what? M80 or M80A1?) That could mean the round is going 3250-3500fps if the +500fps is true.

2. 12% lighter then conventional brass case design. Once again, this is worder vaguely - is that 12% case weight reduction, or 12% cartridge weight production?

3. Projectile is listed as 131gr, whereas the M80A1 is 135gr. Transcription error? New EPR design? Or is this a glimpse of the 7.62 ADVAP Tungsten projectile?

If this is indeed the ADVAP, a 131gr 7.62 suggests the 6.8 ADVAP could be lighter than the 135gr we've been using for our estimates. 

gatnerd said:

Projectile is listed as 131gr, whereas the M80A1 is 135gr. Transcription error? New EPR design?

"The [M80A1] bullet measured 8.48 grams, or 130.87 grains."  Taking a Look Inside the Army's DEVASTATING New M80A1 7.62mm Round -The Firearm Blog

Ah thank you stan, I had forgotten the M80A1 was 130gr / transposed 135gr with all of the 135gr ngsw talk we've had.

So then almost certainly M80A1 is the projectile. Which means if +500fps (seems almost impossible) that would be going ~3500fps from a m240. 

Yeah, I am skeptical of their weight and velocity claims being versus M80A1.

Although the slide shows an M80A1 round, I'd bet they're comparing to M80.

How did they get their accuracy assessed? The standards for the US M4 barrel is 10 shots out of a barrel, in a barrel fixture, =< 4MOA. Did the Soviets use the same testing procedures, or something different?

gatnerd said:

1. +500fps claimed (vs what? M80 or M80A1?) That could mean the round is going 3250-3500fps if the +500fps is true.

The 131 gr bullet seems to be the M80A1, and in order to achieve ~111 inches of drop at 600 yards you need to push this bullet at 915 m/s / 3000 fps which is totally into the realm of the M80A1 cartridge with a ~20" barrel. The powley computer is predicting a MV of 2995 fps @52,000 CUP with this same bullet and barrel length.

By the way, increasing the MV to 3500 fps (or 1067 m/s) will give you ~196 cm of drop at 600 yards, or 77 inches, which seems to be what is claimed on SIG's chart.

Pressure estimates is 71,000 CUP for 3500 fps out of a 20" barrel.

The comparison seems to be between the current M80A1 (131 gr @3000 fps) and the M80A1 +P+ (131 gr @3500 fps).

Not sure if a "5.56 x 40 mm +P+" would be a good idea (because the AR-15 bolt will be probably out of its limitations), but launching a 64 gr / .224" bullet with a C7 of 0.208 at nearly 3400 fps from a 14.5" carbine would be an interesting feature.