HSwMS John Ericsson was the lead ship of the John Ericsson-class monitors built for the Royal Swedish Navy in the mid-1860s. She carried a pair of smoothbore 15-inch (380 mm) Dahlgren muzzleloaders in her turret. Each gun weighed approximately 42,000 pounds (19,000 kg) and fired 440-pound (200 kg) solid shot and a 330-pound (150 kg) explosive shell. The massive shells took 5-6 minutes to reload.