I concur!

He already got the thread locked once. Quit encouraging shitty behavior and let it go.

Please ^^^

I have a ton of JP bolts and carriers. The bolts are all 9310 mostly DLC and a couple chromed bolts. The carriers are all nitrided stainless. The carriers are all smoother everywhere than any other carrier I have owned with the exception of a nickle/Teflon carrier from an LWRC which has I believe is 8620 with an uncoated or chromed dual extractor spring 9310 bolt. I also have milspec bolts and carriers which are C158/8620/parked with chrome lined carriers. It is really not even close which has the smoother finish. A cheap carrier will have a rough internal finish, regardless of the surface treatment. I don't buy cheap nitrided BCG. Those all seem to have multiple dimensional issues on top of everything else discussed here.

As for nitrided barrels not breaking in... if that were true (which it is not) then how would the barrel ever wear out? How could you break in a chrome lined barrel?

As for what happens to a barrel after wearing through the nitride... its the same as every other barrel where the finish is worn through. Nitrided barrels just don't break in as quickly as untreated 416 stainless barrels, which annoys competitive shooters. What eventually wears in and then wears out is the underlying steel. Do people think that your buned out throat moves forward with horizontal groves somehow preserved by nitriding? Ridiculous.

I remember reading somewhere about the testing of modern powder formulations that essentially helped to add nitorgen into the barrel steel and sort of "nitride" the barrel a bit as you shoot, to prevent barrel wear. They worked on all barrel types but they worked especially well to improve the life of already nitrided barrels making them almost last longer than chrome lined barrels. Can't remember for the life of me where I read that, but I swear it is a thing.

This subject is discussed briefly in Principles of Firearms by Charles Balleisen (published 1945) and might be discussed in Thermodynamics of Firearms by Clark Shove Robinson (published 1942, I think).

There is carburizing and nitriding occurring with every shot, but it is not serving to enhance wear characteristics.  If you've fired 30,000 rounds out of a single barrel, you've exposed it to those conditions for a mere 25 SECONDS.  That isn't enough to compare to a 5-hour salt bath nitride, or a 40-hour ammonia nitride cycle, and it gets sandblasted with every subsequent shot anyway.

There are chemical compounds deliberately added to the propellants of large guns that reduce the temperature and erosive action of the gases.  I don't remember what they are, but I'm pretty sure Lysander has mentioned it recently.

I can kinda confirm this. I don’t know much about metallurgy, but I have destroyed a few barrels by use. I’ve noticed that when I borescope barrels, the nitrided ones often appear to be poorly made by that purely visual metric. And the railroad tracks don’t go away after 5 digit round counts, no matter how much firecracking is shown near the chamber or how far forward the rifling has been pushed. A couple inches forward of the chamber, and the imperfections seem untouched. But it may be that that speaks more about the underlying quality than the coating/conversion.

I’ll let the rest of y’all argue a while longer about why that may be, or why I’m wrong or have an insignificant sample size.

“Milspec” doesn’t mean the same thing in the commercial market as the equivalent-ish terms in the military market. I often avoid commercial products that use that word in the description because of that. The translation is “this is the cheapest garbage we can turn out, and it in no way meets acceptance standards for any military organization, nor is it made in the same way or using the same processes, but it IS black”.