gatnerd said:

The standard M4 of the US army is just button rifled 4150cmv, chrome lined, and reportedly starts to see accuracy degradation at 6-7k rounds. A good 4150 CHF barrel is hoped to go to 20k rounds. Meanwhile this 416 is still holding 4moa after 67,000 rounds:

The 1970s era soviet AKM cal hold the 4 MOA after 25-30K rounds of steel-jacketed military issue ball ammo, provided it was maintained properly

the AK-74 is expected to have a minimum barrel life of 10K rounds with mix of 1 tracer to 4 ball rounds; in real life, you can get between 15 and 20K ball rounds trough the '74 before it starts keyholing, and that's with the steel-jacketed 5.45 ammo which is much more unforgiving to the barrels than the brass-jacketed 5.56

and IIRC the standard barrel steel there is the equivalent of the German 41CrMo4 steel or US 4140, and the barrels are cold hammer forged since the 1970s

Great to info, thank you.

It definitely seems cold hammer forging plays an important role in barrel life.

The M4 won’t start keyholing at 6-7k rounds, but rather that’s when accuracy and velocity starts to decrease outside of spec.

Whats frustrating is this is largely due to the M4 TDP not being updated. 
 

FN had the contract for M4s for a while, and had to button rifle them, despite FN being known for their CHF production (they are a huge OEM for barrels in the US). This created a bizzare situation where all military M4s were button rifled, while all of FNs civilian AR15 barrels were CHF.

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.