Here's one I did tonight after the wife went to bed.
Here it is, at 12:45am.
Black acrylic with a little trick I came up with. I get key machine shavings from the hardware store, which are pretty much entirely brass fibers about 1/16" long, as well as some brass dust. On this one I did layers of CA, sprinkled on the shavings and packed them into the grooves, more CA, more shavings, etc. Then turned it, sealed the brass up with a final coat of CA, turned it flat, then wet sanded and polished. Took twice as long as any of my other calls have, that is for sure. Kind of wishing I hadn't made two brass rings on the insert but for a first try I'll call it a learning experience. Next time I'll do one ring on the insert to match the look of the barrel.
No idea how it sounds...Can't try it while the wife and kids are sleeping.