Initially designed for use with the Connecticut -class of pre-dreadnought battleships, the Mark 5 continued in service aboard the first generation of American dreadnoughts. The 12-inch (305 mm)/45-caliber Mark 5 naval gun was designed as an incremental improvement upon the preceding American naval gun, the 12-inch/40-caliber gun Mark 4. [1] .

The mortar could fire two types of shell, a heavy armour-piercing shell with a delayed action fuse weighing 384 kg, and a lighter 287 kg shell fitted with an impact fuze. The light shell was capable of creating a crater 8 meters wide and 8 meters deep, as well as killing exposed infantry up to 400 m (440 yd) away.

The 12-inch coastal defense gun M1895 (305 mm) and its variants the M1888 and M1900 were large coastal artillery pieces installed to defend major American seaports between 1895 and 1945. For most of their history they were operated by the United States Army Coast Artillery Corps.

Unexploded 30.5 cm (12") APC shell that struck HMS Defender during the Jutland (Skagerrak) Battle. This was fired from the German 3rd Squadron and ricocheted off the water before hitting Defender. Note that shell has lost its ballistic cap, AP cap …

The barrel is 3.05 meters long (called "L/10" in Army terminology) and has a caliber of 30.5 centimeters to fire a massive 305mm shell at range. The barrel allows an elevation range of +40 to +70 degrees, and reloading proved to be a time-consuming process with only one shot every 3.5 minutes or so.

The Imperial Japanese Army (IJA) 305mm (30 cm) Howitzer Type 7 (1918) was a low-velocity howitzer firing a large shell at a high-angle shell.

Very high muzzle velocity was to have given this gun an exceptionally long range, but probably at the cost of a very short liner life. Design of this weapon started in 1938 at the Metal Factory, but was not finished before the start of World War II and no guns are known to have been started.

The Obukhovskii 12"/52 Pattern 1907 gun was a 12-inch (305 mm), 52- caliber naval gun. It was the most powerful gun to be mounted aboard battleships of the Imperial Russian Navy and later the Soviet Navy during both world wars. It was later modified by the Soviets and employed as coastal artillery and as a railway gun during World War II.

Designed to fire the new "super-heavy" AP projectiles, their side belt armor penetration at 20,000 to 30,000 yards (18,290 to 27,430 m) was almost identical to and the deck plate penetration better than the larger 14"/50 (35.6 cm) guns used on U.S. pre-treaty battleships.

The 12-inch (305 mm)/45 caliber Mark 5 naval gun was designed as an incremental improvement upon the preceding American naval gun, the 12"/40 caliber gun Mark 4. [1] . As such, it was a very similar weapon, having been lengthened by 5 calibers to allow for improved muzzle velocity, range, and penetrating power.