WBB, I've not noticed a lightening of the color. The majority of my rifle shooting is with a 1970-ish Sako and a same-vintage Weatherby. Dunno if it's maybe the type of bluing or what. I shoot a lot more pistol than rifle, though, and the majority of that was with a Parkerized 1911 and now a Series 70. I have an old Model 12, but it didn't have much finish when I got it.
Art