Blueing a new rifle?!

[Beiruty]

Yep, I was doing my initial grease removal and cleaning of my new SIG 556 (BTW, I believe it was shot couple rds at factory for testing) and had to remove the quad rail just to see how it is removed. I guess I will never remove the quad rail again, it was pure metal-to-metal sticky business. As a result, I have new 1/4" of gun-blue rubbed off on both side of the receiver where the quad rail slide back. In addition, where the expended brass exit the receiver another 1/4" blue is being rubbed off.

I didn't expect to see a bare metal on new rifle. What kind of coating if any do SIG uses anyway? Do you think I should use some touch gun-blue?
Also, I was advised that some SIG owners use an electric tape to cover the exit port so it would not be scratched by the exited brass. The tape is removed after the range and before cleaning the rifle.

Maybe this http://www.topgunsupply.com/birchwood-c ... black.html" onclick="window.open(this.href);return false; is a good solution.