I suspect that they mean Gun Metal and Satin Gray, but is there any difference or is it just two names for the same thing? Sorry if it's been covered before, but search didn't provide an answer.
I do not have either however the pics I have seen they look the same to me.
maybe just a marketing tactic for 2 groups of folks. I think "gun metal" might be for folks like me and the SG intended for folks that are of a higher class.
They still look the same to me.
Topper
As far as I can tell they are the same.
There is some variation in hue etc but just like HA it's the lighting that makes the difference - it's best to compare side-by-side and not using photos.