Gathered here are some of the historic guns tested at Dahlgren. The 16-inch, 28.8-caliber gun, though not in its original configuration, is the oldest American battleship main battery gun in existence. It was converted to its present configuration so that Dahlgren would have a dedicated 16-inch gun for use at Plate Battery for testing armor-piercing projectiles, base fuzes, and armor plate. The 8-inch, 55-caliber Mark 15 gun was used to proof fire 8-inch Mark 15 bag guns from the 1930s through the Vietnam era, when the last heavy cruisers using the 8-inch Mark 15 guns were retired. The 16-inch, 45-caliber barrels came to Dahlgren in the mid-1940s for proof testing and were re-gunning assets for the battleships of the North Carolina and South Carolina classes.