In 1895, the British developed a 5 inch howitzer for it's field forces.  It was the latest thing, using smokeless cordite propellant and  emphasizing explosive shrapnel shells.  These guns decimated the  Dervishes at the battle of Omdurman in 1898 before the bad guys even got in range of the British Maxim guns, effectively winning the battle before it even started.

The gun was one of the new breech loading guns using an early 3 motion interrupted screw, fired a 50 lb. shell, and had an effective range of 4,800 yards, or almost 3 miles.  Due to a change in the ammunition during the Gallipoli campaign, the range tables weren't updated, making the gun relatively useless because the gunners couldn't hit what they were shooting at. The gun was already obsolete by WW1 anyway.

Which brings us to today, where the 5 inch gun has made strides not even imagined by it's 19th century designers.  BAE, Lockheed Martin and Science Applications International Corp. (SAIC) are working on a GPS guided LRLAP (long range land attack projectile) designed to be fired from the Mk. 45 5 inch gun.  This projectile is being developed for the US Navy's Advanced Gun System (AGS) for it's newest Zumwalt class destroyers and other land guns systems.

This projectile and gun system is effectively a ballistic missile that can engage targets up to 70 nautical miles away.  And since they are guided by GPS, they really can't miss.  Where the old British 5 inch gun had a muzzle velocity of 800 fps, this rocket propelled shell initially left the gun at 12 g's, but this has been softened to 8 g's to help the electronics survive.

The goal is for this shell to be fired from a standard 155 howitzer, and in this configuration, four gun emplacements could cover 80% of Afghanistan, for example.