This is a replica of a full charge for the USS Iowa's 16-inch guns, which gives you some idea of how incredibly powerful they are.

The 5 powder bags are mock-ups, but the shell itself is real --- albeit a training round, whose ballistics simulate those of a High-Capacity ("HC"; the US Navy term for a High-Explosive round) projectile. You can tell that it's a non-explosive training round by it's blue paintjob, which is probably why the Navy allowed it to be put on display in the first place.

The Iowa class Battleships have been issued a range of projectiles over the years, but the most common are the Mk.8 AP (Armor-Piercing) round, and the Mk.14 HC round. These weigh 2700lbs and 1900lbs, respectively (I previously said 1800lbs, which was apparently a mistake --- they're even heavier!). It was a Mk.14 that the Iowa herself fired, when achieving the record of the longest-ranged 16-inch shot in history in 1988.


I've linked to this page in my comments before, but it's worth a refresher to appreciate how powerful this ammunition is;
http://www.navweaps.com/Weapons/WNUS_16-50_mk7.htm


Finally, it's worth noting that due to the colossal weight of the one-ton projectiles and 200lb powder bags, the cycling loading processes of the Iowa class Battleship's main guns is heavily-automated. The gun crew mostly provides oversight and makes minor manual alignments, but otherwise virtually never actually lifts or pushes anything.