Combination Post here.
I have one of the first Sig P320-X5's out there, and it came with an uncoated stainless barrel. They later changed to a nice black DLC coating. I've been tempted to do a TiN coating like some custom Glock barrels use, and I think STI uses it as well. I couldn't really find a good company until I came across Brazen Firearms out of Ohio. Prices were good, and reviews were great. I sent them the barrel and tungsten guide rod out of my gun, had them back in about two weeks. Coating is done great, and I expect it to hold up decent. This is purely a cosmetic mod for me, but maybe some of the grime that gets on the barrel will wipe off easier. https://www.facebook.com/BrazenFirearms/
Second up, was Alma Cole who did some grip work for me. I was previously running some skate tape grip, but wanted something less bulky and more permanent.
https://www.facebook.com/AlmaColeShooting/
Pictures: https://imgur.com/oLUZW7l https://imgur.com/gIaDToL https://imgur.com/HQxJdgC https://imgur.com/RGNJRa3 https://imgur.com/dsphVEG https://imgur.com/egr2FhU