The Ukraine War was yet another reminder that stockpiles of weapons built up in peacetime tend to contain fewer artillery shells than are required when there is a war. To make matters worse, the production capacity for additional munitions is usually neglected too. That means when you discover your war reserves were too small, you find that existing production facilities are unable to quickly make up for the shortages. This is not a new problem in democracies because peacetime politicians back spending on items popular with voters. War reserve munitions stockpiles and production facilities are not popular with voters because they are expensive and do not address any immediate need. That changed, temporarily, because of the unique experience in Ukraine. While Ukrainians did all the fighting, NATO nations, mainly the United States, supplied most of the munitions and many of the weapons Ukraine needed to stop the Russians and to push Russian forces out of Ukraine. The most common NATO artillery munition was the 155mm shell. The Ukrainians found these to be more reliable and effective than the Russian designed 152mm shell they were still using. When equipped with 155mm artillery and ammunition, the Ukrainians found they had an edge over Russian artillery.
The crucial Ukrainian artillery innovation was locally developed and built UAVs locating the Russian artillery using new Ukrainian-developed communications and fire control software. This was able to immediately provide Ukrainian artillery with the target locations. Even unguided 155mm shells could destroy or disable Russian guns, especially if they were firing in large groups from the same location, as Russian tactics dictate. More importantly, the new Ukrainian tactics dramatically facilitated almost instant use of massed fire on newly identified targets by any artillery piece in range. This is similar to Uber and Lyft software for sharing vehicle rides between drivers and users. Such immediate massed fire by two Ukrainian artillery brigades stopped the Russian attack on Kiev early in the war.
The Ukrainians went further and used their superior battlefield surveillance capabilities, some of them supplied by NATO, to locate the Russian artillery munitions storage sites. These stockpiles supplied the Russian artillery units firing on the Ukrainians. These storage sites were increasingly found and destroyed. The best the Russians could do was move these storage sites further away from the front line. Because Ukrainian GMLRS guided rockets had a max range of 85 kilometers, the Russians had to move their storage sites to locations more than 80 kilometers from the front lines. This required more trucks to transport the munitions over longer distances. The Ukrainians identified and destroyed a lot of these trucks during their long journey. What this all meant was that, after a few months Russia had lost any artillery advantages it had. Ukrainians now had the edge when it came to artillery support and counterbattery capabilities, which is the ability to find and destroy enemy artillery before they can do the same to you.
So far, the U.S. has sent nearly a million 155mm shells (50,000 tons) to Ukraine and there is not much left but the U.S. war reserve for possible conflicts in Korea or the Middle East. South Korea had larger stocks of 155mm shells and sold 100,000 of these to the Americans to maintain their war reserve. South Korea stipulated that none of these could be transferred to Ukraine.
At this point the Ukrainians were able to use all the 155mm shells they could get. At the same time the United States and other NATO nations had sent most of what 155mm ammo they had. All NATO nations were producing as much as they could, but production capabilities were only sufficient for building a small war reserve of shells with a shelf life of at least a decade and often more like 15 or 20 years. This persuaded American politicians to allocate over half a billion dollars to expand 155mm shell production capabilities from 14,000 shells a month to 20,000. By 2025 the U.S. will be producing 40,000 shells a month. Ukrainian forces normally go through that in less than two weeks. Other NATO nations are also increasing production capabilities because the next time it will probably be NATO troops doing the fighting and dying.
NATO standard 155mm shells each weigh 45 kg (100 pounds) and have about 9.1 kg (20 pounds) of explosives. This makes for a bigger bang than Hellfire or TOW missiles, but much less than smart bombs. There's also the 227 mm GMLRS guided rocket, but this carries over 68 kg (150 pounds) of explosives, about half the bang of a 227 kg (500-pound) JDAM GPS guided bombs. The GPS-guided 155mm shell and MLRS rocket each cost over $50,000 each. The GPS guided 155mm shells are expensive but popular because these GPS artillery munitions are available to the troops 24/7, and the need for fewer rounds per mission means there are fewer problems with running out, or low, on supplies shells.
A less costly alternative to the Excalibur GPS guided shell is the ATK fuze. These are screwed into the front of an unguided 155mm shell. The ATK approach is somewhat less accurate than Excalibur shells but that has been found acceptable in combat situations. This was seen during 2017 in Syria where a lot of ATK equipped 155mm shells were used to support Kurdish troops taking the city of Raqqa from ISIL (Islamic State in Iraq and the Levant) forces. While the ATK fuze is cheaper, it is still a complex bit of tech and production facilities are not available to build a lot of them in a hurry. Excalibur stockpiles were larger and most of these smart shells were sent to Ukraine and used in situations where you wanted to hit the target accurately and without warning. With unguided shells, you have to fire several to make sure you hit the target. The first shell to hit the target area warns the enemy more shells are coming and immediately seeking shelter means fewer troops in the target area are killed or wounded.
Another problem everyone has is that the shelf life of most munitions varies from 5-20 years, depending on the component, such as the fuze, electronics, batteries or propellant used to assemble a shell. Shells and rockets use various types of explosives, notably as propellants, that degrade over time. Western nations spend a lot of money to remove elderly munitions by recycling them. This is expensive but it is a major reason why Western munitions are more reliable and less dangerous for users.
Russia takes a different approach. They know from experience that their 152mm shells gradually become less reliable after ten or twenty years stored in a warehouse. Older shells don’t function as designed. That means more shells that are inaccurate or don’t detonate. That means more duds. For shells older than 20 years there is greater risk of a shell exploding in the gun or shortly after fired. This causes death or injury to the gun crew and anyone else nearby. Senior Russian commanders consider this an acceptable risk in order to win.