Now for the easiest part, weathering the aluminum barrel. I started by scuffing it up with some light grit sandpaper. Nothing too bad, just enough to take the shine off.
I then mixed up some Applebarrel acrylic black paint and some thinner to make a wash. You want it to be the consistency of water. You can use water to thin it, but I recommend windshield wiper fluid or glass cleaner. Slather it all over the barrel until it is good and drippy then blot it with a paper towel. Wipe it in different directions until the paint is just about gone. Then repeat. After 2-3 times, the barrel should start to darken and get some good patterns in it.
If you overdo it, wait until it is dry and then hit it with a scotchbrite pad to take the paint off. Under normal conditions, the paint should last forever without any sealer.
A stepped disc was glued on with JB Weld. I can't tell you how much I hate JB Weld, but it gives a good bond. The stuff has the consistency of toothpaste and when clamping parts, they tend to slide. It also dissolves paint! Luckily, the gun is weathered, so no one will know the difference. I wanted the scope rail to look like it was an add-on piece, so I left it in pristine condition to give some contrast to the weathered 'Sterling'.
The scope with the holes filled with Magic Sculp and sanded. The caps can be removed. The things the caps are sitting on are too tall so I thought I would shorten them. Each one has a screw in it, but they are gorilla glued in. You can see the damage where I tried to pull one out with pliers.