Designed by Petersen, a man John Browning declared the most gifted gun designer ever. The unusual feature of these if the fact the entire magazine tube mechanism moves when the action is cycled, unlike other pumps that simply has a stationary magazine tube that has a cartridge cuttoff that trips when the action is cycled. Having owned and studied quite a few of these over the decades, I firmly believe these to be on of the top repeaters ever built. Resist the urge to disassemble it often. I have seen quite a few ruined by excessive, unnessasary disassembly.