MG brass

One idea that came to mine is to use insulated wire gagued approximately the size of a spent round, using wire strippers, strip the insulation to scale length of a casing, fill one end with putty or super glue, then paint it a brass color. It migh seem a little time consuming, but it looks a little more realistic having shown one end of the casing open where a slug once was. Anyway good luck and have fun....

Great idea, must remember that for a future project..

That's a lot easier than what I used to do 30 years ago: stretch sprue and THEN paint it brass or gold and cut it. A real pain. Go for the wire and snip it. Looks great, it's cheap and simple.

That's actually one of the most common methods of simulating brass casings. You're definitely on the right track.