I'm not implying that HK is building rifles to the "M4" TDP. They're obviously building M27s according to the HK TDP. Just like FN isn't building M4s to Colt's TDP. FN is building M4s to their own TDP.
From what I understand, HK doesn't use chrome lining. Do you know if this is true?
As long as people realize it's a pretty high standard. I find it ironic critics lambast the M4 as being the minimum standard, yet ignore the fact the highly touted M27 falls in the same category.
(It's obvious to me, you are
not one of those critics
)
To be clear, I don't think companies like BCM & SOLGW are turning out inferior ARs.
They just don't build cars like they used to. For that, I'm eternally grateful!
From the technical dives into C158 versus other alloys that I've seen, there isn't much improvement. There's evidence that other alloys have their own downsides. But, there's evidence that some geometric changes show improvement in longevity, such as found in the KAC bolt.
I've also seen arguments that there's little advantage in extending bolt life because on the average, bolts and barrels have a similar round count before needing to be replaced.
I don't hold to the idea ARs cannot or should not be improved. What I'm saying is, the current M4 as built by Colt isn't objectively as outdated as critics would have us believe. Colt ARs have good, solid bones. (I have no first hand knowledge about FN ARs. I assume they're delivering a fine rifle to our military.)
True, Colt doesn't offer as many configurations as others. Whether or not the configurations offered by other companies are better or more innovative is subjective.