Looks good!!! And I like the idea of trying different materials in it. Each should change the harmonics and possibly be a way to tune it?
Personally, I would love to see a gas block with an adjustment rod extending out so that it also serves as a strut, just like on the M14. I have an adjustable gas block and my strut almost lines up with the adjustment screw in it. It wouldn't be that difficult for some one to just go ahead and connect the two.