There was a thread on here talking about containers for extra powder loads and I liked the idea and made myself some with slight modification. As suggested I used a 270 brass case but was concerned with these being noisy ratting together. Some guys that duplex said they where taping two cases together and the tape would also get rid of noise,but I thought I would go a little further so I added electrical shrink tubing to mine.Personally I don't duplex but it would work the same with larger tubing,here is a pic.