For the life of me I cannot find exactly what SIG barrels for these upper kits are done in: nitride or chrome lined? Or nothing? SIG's own website doesn't even say, nor do the numerous adds at vendor websites. Why are they so cagey about it?
Like this one:
UAMCX-16B-556-TAP
https://www.interstateguns.com/sig-s...b-556-tap.html