Shot 40 rounds through the Cross and the stock barrel today, bolt head pic below, no cleaning. Was hot as dogs balls in Alabama out there today but enjoyed shooting it none the less. A bit different than the AR10 and this'll take some rethinking on shooting technique. It's brutal compared to the gas gun but I like it! I started to get the hang of it towards the end and will be ordering a few 10 round mags so I'm loading less and shooting more, LOL. Needed a bigger rear bag too. Groups were all over the place and it almost made sighting in the scope pointless. The last 20 started to see the group sizes fall but I'm not there yet. I can now see why adding weight on a chassis gun makes a difference.
Just did a mild carbon clean on the barrel and bore scoped it. No real copper buildup that I can tell but I don't have the best bore scope. I can see copper in the grooves but not in the rest of the barrel. Looks more "polished" than it did fresh out of the box when I scoped it.
On the bolt head coating, I assumed it was an advanced nitriding process like what Rubber City Armory uses on their BCG's transforms the surface of the metal. So no idea what Sig is using. The rest of the bolt assembly is pretty slick and sort of reminded me of a cheap DLC but maybe it's just some sort of high temp paint. I washed everything and lubed per the factory manual prior to hitting the range and the action was great. Trigger too...I have it adjusted on the light end and dry firing, I honestly couldn't tell the difference adjusting it to extremes. But on the firing range, it's definitely lighter and more "precise" than my gas gun triggers which are set at 4 pounds. I like it. Totally get the two-stage trigger now.
Oh, my safety has the "in between" position as well. Almost like they originally designed it to be a 60 degree throw. There's a definite detent halfway through its travel.