Duplication Exploit

This duplication exploit involves putting a timer on a piston via Redstone repeaters and having the piston move a chest. If you activate that timer and are able to pull out items out of the chest at the exact time the piston moves the chest, you can take out that item, while having that item still remain in the chest. Using this exploit I was able to duplicate a whole stack of diamond blocks which I would see as unfair on some pvp realms I play on.