The Mossberg 590A1’s design is the culmination of over 50 years of shotgun engineering. The Mossberg 500, developed in the early 1960’s, served as the model for the 590, which the American company evolved even further until they achieved the A1 . Since the A1 is built so similarly to the standard 590, we will only gloss over the overlap of their designs, and hopefully focus more on its standouts.
One of the A1’s most important achievements is its MilSpec qualification. Through rigorous testing, the A1 passed the U.S. Military’s assessment allowing it to be used by our military personnel all around the world. Just to put this into perspective, the 590A1 is the only pump action shotgun ever to pass MilSpec 3443E.