Thsi was the last gun I painted, not to long ago. Its a S&W M&P15 T something or other.
As far as context......
I used to hunt birds a lot, especially doves in the fall. The difference when in the open, between a gun thats cammied and not, especially when you are, is pretty obvious right away. When I use a gun thats been painted, I almost always get a lot more shooting, and shooting thats a lot closer.
Ive been painting things since the 60's, and its a passed down thing, not something I dreamed up. Its really nothing new, but maybe its a regional thing, I dont know.
As far as the paint being detrimental to the gun, I have never found that to be the case. If anything, its always been a plus. Ive removed paint from shotguns that were painted 25+ years ago, and used pretty much every season, and there wasnt a speck of rust or wear where the paint remained on the gun, which was 95% of it. Those spots where the paint wore off due to handling and use, were the only points that showed wear or minor rust. The paint protects the gun way more than it damages it, assuming you use the right paint.
Youre really not devaluing anything, especially if the paint can be completely removed. Painting with something that needs a bead blast to get off is totally different. I painted my HK MP5 in ASAT back in the 90's, and left it that way for a number of years. I used to hang the gun on the coat hook over an ASAT coat, right in the open, and not one person who walked by, or stood next to it, ever saw the gun, unless I pointed it out. Hide in plain sight on steroids.
After those couple of years, I got tired of it, and stripped the paint off, with no damage to the gun.