The demand for naval guns is driven by two requirements, each at the extreme end of the performance spectrum. One is for artillery whose ranges go well beyond those of the big guns used in World War II. The average range of naval guns then was 35-40 km. (22-25 mi.), with the 18-in. (46-cm.) guns of Japan's Yamato-class battleships capable of firing 1,460-kg. (3,218-lb.) projectiles 26 mi. The other requirement is for small-caliber weapons to defend against airborne and asymmetric threats and for use in missions where navies confront pirates and other criminals.

These requirements are leading to developments that, in the case of big guns, gradually push the envelope of ballistic capability. U.S. and European navies are foregoing radical changes in gun design and ammunition for incremental improvements that increase range, payload and accuracy. In small guns the emphasis is on remote operation, sophisticated target-acquisition systems and rapid, sustained rates of fire.

When it comes to big guns, the U.S. Navy still relies on BAE Systems' 127-mm./54-caliber (127/54) Mk.45 5-in. gun, the latest version of which is the longer-barreled 127/62 Mod 4. None of the exotic long-range guns or guided ammunition the Navy has been developing (think rail guns and missile-firing hybrids) is near deployment.

European countries have attempted to develop high-power 155-mm. naval guns. The 155 is preferred because it is the caliber of their biggest army guns and procurement officials believe this would increase standardization, commonality of ammunition and reduce operational costs. France and Germany studied the concept, but only the U.K. is working on it.

The Italian navy is the only country with a new long-range naval gun program nearing service, with a 127-mm./64-cal. mount from Oto Melara, coupled with the company's long-range Vulcano ammunition in guided and unguided versions. Italy will use the 127/64 lightweight gun on Fremm frigates. The weapon may also be fitted on the French navy's Fremm frigates, budget permitting, and has been ordered by Germany for the new F-125 frigates. The Royal Netherlands Navy is adopting the Vulcano ammunition for its upgraded 127/54 Oto Melara mounts, and at least three other navies are discussing acquisition of the 127/64 gun and ammunition combination.

In the U.K., BAE Systems proposed the 155-mm. TMF (Third-Generation Maritime Fire Support) system to the Royal Navy. This consists of the company's 114-mm. (4.5-in.) Mark 8 Mod 1 mount/turret, fitted with the British Army's AS90 155-mm./39-cal. gun, also made by BAE. The modification makes the mount 2 tons heavier (24.5 tons) and reduces the rate of fire to 12 rounds/min., due to the double-stroke loading cycle that stems from modular charges.

The system is proposed for the Type 45 destroyers slated to enter service with 114-mm. guns and as a retrofit for Type 23 frigates. So far, use of the heavier and longer army-standard 155-mm./52-cal. gun has been ruled out since it would require substantial turret and mount modifications. Preliminary studies have nevertheless been carried out on adapting the gun fro naval use. The only recent improvement the Royal Navy received for bombardment was the introduction, in 2004, of unguided extended-range (ER), base-bleed, high-explosive rounds, which increased range to 27.5 km. from 22 km.

Oto Melara, meanwhile, is producing the first batch of the new 127/64 guns with various improvements, following tests on the Bersagliere frigate with the earlier 127/54 lightweight gun. The production turret now weighs less than 29 tons and is capable of firing more than 35 rounds/min. The gun has a "peppered" muzzle brake (similar to those on land-based guns) with an aluminum shield, which replaces the glass-reinforced thermoset polymer version. The choice was made to reduce costs and improve maintenance without affecting radar cross-section qualities. Radar-absorbing material is still used in critical areas.

The 127/64 relies on an advanced ammunition-handling system, consisting of four revolving drum magazines holding 56 ready-to-fire rounds of more than four different types (see diagram). This permits flexibility in ammunition selection and a high rate of sustained fire. The drums can be reloaded while the gun is firing, due to an innovative semiautomatic system that moves ammunition from the magazine. In the current configuration the magazine holds 350 rounds. The Italian and German navies have ordered the system, and Oto Melara is developing an automated version.

The gun is one of the few of its caliber capable of three missions: antiship and antiair defense and bombardment. It has a GPS system and Doppler radar that measures the velocity of each round to increase the accuracy of successive rounds. The mount includes a Vulcano ammunition programmer that gives each shot its mode of attack prior to firing.