Since the late 20th century, most NATO armies have adopted 155 mm weapons as an all-purpose standard. They are seen as striking a good compromise between range and destructive power, while using only a single calibre simplifies logistics. This has led to the obsolescence of larger calibre weapons such as 175 mm and 203 mm, although some militaries retain 105 mm weapons for their light weight and portability. Russian guns and those of former Soviet bloc countries tend to use 152mm weapons in similar roles.
Naval warfare
Since the end of WWII, 155 mm has not found any use among naval forces despite its ubiquity on land, with most NATO and aligned navies using 76mm, 100mm, 114mm, or 127mm guns on modern warships. At one point the British Ministry of Defencestudied "up-gunning" the Royal Navy's 4.5 inch Mark 8naval guns to give increased firepower and a common calibre between the Royal Navy and the British Army. However, despite superficially appearing to be superior due to a comparison of round diameters, when firing conventional ammunition the smaller, 4.5" naval gun is comparable to the standard 155mm gun-howitzer of the British Army. The standard shell from a 4.5" naval gun has the same, if not better, range and carries twice the HE payload of a standard 155mm round. Only by using rocket-assisted projectiles can most 155mm guns have comparable range to the 4.5" naval gun and in doing so by sacrificing the payload. This is because naval guns can be built much more strongly than land-based self-propelled gun-howitzers, and have much longer barrels in relation to calibre. This allows naval guns to fire heavier shells in comparison to shell diameter and to use larger propellant charges in relation to shell weight leading to greater projectile velocities. In addition, even without active cooling, the heavier naval gun barrels allow for a superior sustained rate of fire compared to field guns, and this is exploited with an autoloading system with a capacity of several hundred rounds. The 155mm is superior to the 4.5" naval gun in relation to cannon-launched guided projectiles ; because the 155mm round is fired at a lower velocity it is much easier for their internal electronic guidance systems to survive being fired. The US Navy's Advanced Gun System also uses a 155mm calibre, although it is not compatible with NATO-standard 155mm ammunition. However, since 2016 no ammunition has been developed and therefore the Advanced Gun System is completely unusable.
