Abstract: What is new in the firearm technology: The Twin Chambers Magazine provides double cartridge capacity to feed a firearm than present magazines of the same length. Its separated chambers have a wider internal relation, have perforated guides for the elevators, are synchronized by its mechanism that does not require electric power. This makes 2 independent magazines work together feeding one common mouth, can be use in some firearms without modifications and can be produced for any present cartridge. Its stopping mechanism allows one chamber to begin to work until the other chamber is already empty, working in serial and orderly: first the left one, then the right one. The TCM avoids changing frequently empty firearm's magazines, providing more cartridges and saving time, has a reduced size compare with the drum and spiral magazines, and does not present jamming if it is stored loaded for a long time.