In the 1850s British warships were still armed with smoothbore muzzle loaders, generally of 68 pounder, perfectly adequate to defeat the wooden hulls of the time. Things changed rapidly when HMS Warrior was launched, an armoured ship with steam power, proof against most naval gunfire of the day.
The Armstrong rifled breech loader developed in 1859 seemed to offer the answer, firing heavy steel or explosive shells with more power and greater range than a smoothbore cannon. The shells had a coating of lead to engage with fine rifling, loading was by a wedge breech block retained by a heavy screw. It was found however the system once adopted was fatally flawed, the breech block was very heavy, the screw retainer was unreliable. In the first large scale use of the gun 28 accidents were recorded firing 365 rounds! Back to the drawing board.
The solution was a rifled muzzle loader, wide grooves engaged with studs on the projectiles, no breech meant a huge powder charge could be used and this became the navies gun of choice, manufactured in a wide range of calibres up to 17.72 inch - the famous 100 ton gun of Malta and Gibraltar.
In 1879 the next step was the adoption of the interrupted screw breech, longer guns, fine rifling and a copper driving band on the shell which sealed and spun the projectile, development of these was rapid, to keep pace with the development of the battleship, becoming the 15 inch gun which armed many British battleships.
The pictures below from the museums extensive collection of projectiles show in order - an Armstrong breech loading lead sleeved shell, a RML studded shell and the eventual shell with driving band which is still in use .