I am getting to the end of my build now... I added the window by getting some red gel covers normally used in photography and putting a piece of window tint on it. It gave it the look I was after ... that smoky with a hint of red cover.
I used paint, tea, sandpaper, a brick wall and my driveway to distress the sling. I am happy with the result and it fits the general aging of the gun I have done.
Here is a bad photo...
Next I cut up a toy guns ammo belt and put in the some dummy rounds to fill in the mag.
It's not perfect but I like it!
I also used Silver Rub n Buff to make things look worn down on the corners and edges. The trick to this stuff is, less is more and you have to have to really rub it in! When you think you have it rubbed in buff it some more... once you do this it will not rub off from handling. I apply with my fingers and burnish it with an old t-Shirt.
Lessons learned along the way...
1. The 870 Express is not a perfect match. The shell ejection does not line up perfectly with the original prop as the distance between the trigger and the window must be slightly more. If the 870 trigger is in the right spot on the SPAS cage the window is not. I fudged each slightly to come up with the best scenario.
2. Keeping the hammer retention spring on the 870 is not really viable without some modification to the shrouds, enough modification that it will get into the metal plate cover in that forward area.
3. The barrel of the 870 starts wide and tapers to the the end. Keep this in mind when attaching the slide to prevent binding.
4. Going all metal is heavy! My gun tips the scale at 14lbs and you can feel all of it! Good thing there is a sling!
5. IMO adding the firing lights and sound made what feels like the real deal feel like a toy. In the end I removed these as it took away from the "authenticity".
6. BE FEARLESS! I suffered a very long time of feeling like I was going to mess something up. It's your build and you should go at your pace but don't let that fear keep you from completing what was for me a bucketlist prop.
7. The mounting block is the key! without the mounting block this would have been a much harder build. I am not sure who I originally got the block from but this, for me, saved a huge about of time.
8. Aluminum black did not work. It was quite awful. In the end sanded, etch primer and paint(and adequate dry time) were a much better alternative.
How about a few pics. There will be a little more later but these are hot off the camera...
and a bonus...