I had a LWC that wore np3 really well. My next refinish -- an izzy highpower -- will probably be my chance to try NP3+.
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I'd recommend against the FCN. Especially if you are going NP3 afterward, if you can get the plater to even do it. I would expect adhesion issues to surface in attempting that.
I'd leave it as bead blasted stainless.
FCN is at its best in a wear resistance application, like a gear. Not an impact loaded application, like a gun. Glock gets away with it because their steel is a nice buttery soft alloy.
In a sort of ghastly simplicity we remove the organ and demand the function. We make men without chests and expect of them virtue and enterprise. We laugh at honour and are shocked to find traitors in our midst. We castrate and bid the geldings be fruitful.” ― C.S. Lewis, The Abolition of Man
How can you tell it's custom with no serrations on the arse end of the slide? Duh.
(I can't remember which custom make it was... maybe Les Baer? ...who said that the main reason his guns have FLGRs was because people expect an FLGR on a custom gun.)
That being said, if there was any place where reflections on the rear face of the slide might be annoying, it'd be on a dot-sighted pistol with a stainless slide, so there's that...