Be an informed consumer!

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Here are some pics of the nitrided extension that chipped like glass with the mere touch of a rubber Cratex polishing bit. You can see it on the right feed lip. I've done scores of feed lip jobs where the lips don't match the extended M4 ramps, even with M4 extensions, because the industry is all over the map when it comes to matching these parts up. For those of us who shoot a lot of 68-77gr BTHP's, we like to have a smooth transition there, with no possibility of the meplat catching on the edge of the feed ramps of the extension.

There has been a learning curve for some manufacturers on QPQ/ferritic nitrocarburizing, which is why I think I got this barrel at such a low price. $170 for a fluted, CMV, .223 Wylde chamber seemed about 1/3 of what I should have been paying, but I rolled the dice. I had it in a rifle upper without ramps before, and was planning on moving it to an M4 upper. The index pin was also sharply cut of with grinder marks on it, with no consideration for clearing the female threads of a barrel nut, so I radiused it and made it so that it would perform as expected.

After having a mechanical engineer look at it, he said it appeared to be through hardened, and kept asking me if I had dropped it on a hard surface. There is also some galling on the bottom of the 3 o'clock tooth of the extension, which looks like it could have come from installation with the barrel extension tool. The barrel is quite accurate though.

Tragic. Dented spot looks kind of dirty where the rest really shines.
So let me ask you. If carburizing called for by the mil spec hardens the extension 20 times, 20 times deeper than Melonite which would likely cause through hardening?
On a related topic what are those shiny extensions made from and why are they shiny? Can't possibly be stainless so are they untreated 8620? Why are Armalite extensions parkerized?
LRRPF52 is the Super Moderator of the Grendel Forum, number 1 Grendel and Alexander Arms promoter. I promote the 6.8SPC. He travels the internet to bad mouth the 6.8, the 264LBC and any company that competes with Alexander Arms.