In order to do realistic reflective map, you have to have a weight map linked with it.
An object, can't just through the reflection map (weight map linked) onto a default blinn shader. A color map, base color map, and dirt map is very important.
Base color map: is for define general overall color variation. Some where around the gun handle, you may want to have the color map desaturate a little, the trigger should near to the color of silver (it can shows the age). But remember, Base color map is for overal, no need to get into detail. you can blur everything
Color map is the new detail thing: you may want to combine with the dirt map also, it is totally up to you. i always separate the both, that way i can have more control on 2 maps. How detail, or what kind of detail you want? well, you might want to do some more research, I never did guns b4, can't give you specific suggestions. But mosly, you want to have grunch, on edges, dirts on some sucked in parts, or even your 暗花 can be painted on this map.
However, you need a diffuse map (weight map again) for this color map. Well, this one is kind of tricky. A weight map is to define who is going to show, and who is not. And how do you define where to, and where don't. here is some suggestions (according to Leigh from cgtalk.com) Diffuse map always is the opposite of the spec/reflect map. Say they are all together 100%, if you want your object tobe 70% reflective, then your color map should be 30% showing only. Then you will say, oh gosh, my gun is 90% reflective, then which means only 10% of my color map is showing? which means, all of my work on the color map will be hardly seeing it? Well, the answer is yes, and no. That's why you need a weight map for it.
Where should be, and where shouldn't? For my opinion. The area that your character always touches should be more reflective. since character may give it oilish, or due to ages, it flaten the areas, so that it will give more reflections. In other words, the place that she never touch it will never get reflections. Such as, some area got sucked in, or parts that are hidden, bumps. That's going to show no/less reflections. Which means, the color map is going to show. Area that dirts has, for sure isn't going to reflects.
you got the idea?
I strongly suggest 暗花 should be some kind of paints right? then it should bump up. just a tiny bit, many people cast their bump map too much will reduse the reality of it.
For the scoup part of your gun, i know it is not going to reflect like the gun itself. however, you always wnat to get a spec map for it. same idea, showing part should get more spec....etc
hope it helps. if you don't understand anything. post the resourse, and i can do a little demo to you
好正啊! 
