In the last few months Ukrainian troops have noticed reduced use of artillery by the Russians. Better yet, more of the Russian shells and rockets are duds and don’t explode when they hit the ground. Ukrainian troops learned how to use their artillery ammo carefully because NATO nations did not have as much to provide as Russia already had. That’s because the Russians maintained larger stockpiles of munitions and had a lot older stuff that could be used somewhat safely by Russian artillerymen, but were more likely to fail to explode to land where aimed.
For the first six months of the war Russia was able to fire a lot more shells and rockets at the Ukrainians than the Ukrainian were capable of. That changed because Russia, like the NATO nations supplying Ukraine, is running out of artillery ammunition. Existing inventories are largely gone and munitions firms worldwide have all the business they can handle. Russia does not have as much capacity for manufacturing enough munitions to replace what has been expended or destroyed by the Ukrainians, who carefully attacked all Russian ammo stocks they could find and hit. Plus they captured a lot and promptly used those on the Russians, notably after their breakout from Kharkhiv this fall. Russia has few foreign sources of munitions and those sources have encountered problems. For example, North Korea sold Russia large quantities of shells, much of it near its “use by” date. These munitions were moved to Ukraine via the Trans-Siberian railroad. Russia has had problems lately with that rail line and that has delayed some of the North Korea munitions shipments. Another source was Iran, which didn’t have as much to spare as North Korea but was able to get it to the Russians quickly.
That left neighboring Belarus, which Russia has pressured to enter the war to assist Russian forces in Ukraine. The Belarussian leader is pro-Russia but most Belarussians are not and support Ukraine. Because of that, Belarus cannot send troops into Ukraine but Belarussian ammo stocks and manufacturing capabilities are available. As with Iran and North Korea, Belarus has to be paid
One of the problems Russia has is that the shelf life of most munitions varies from 5-20 years, depending on the component (shell, fuze, electronics, batteries or propellant.) Artillery 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.
When the Cold War ended in 1991 Western nations were able to safely dispose of munitions that were too old to be safe and reliable. Russia had more of these munitions and little cash or sense of urgency in safely disposing of their elderly artillery shells and rockets. Storage facilities containing these expired munitions eventually began to randomly explode in a spectacular fashion. Russia then sought to dispose of the oldest and most unstable munitions in controlled explosions that did not destroy structures and kill or injure nearby military or civilian personnel. This disposal process is still underway and Russia keeps track of how old munitions are and knows which munitions recently passed their use-by date and can be safely delivered to artillery units for use. This is one reason why Ukrainians experience many Russian shells and rockets fired at them that are very inaccurate and often do not detonate when they land. For Russian artillerymen, a few of these shells and rockets explode when fired, often killing or injuring members of the gun crew.
After 1991 major nations continued maintaining millions of tons of munitions as War Reserve Stocks, to provide a 30–60-day supply of ammo for the opening stages of a major war because it take over a month for fresh supplies to begin arriving from factories. Constantly replacing elderly munitions from the War Reserve leaves you with a constant supply of old stuff that has to be used or disposed of. Not too long ago, the old munitions would be dumped at sea, usually in very deep water. But that is not considered ecologically correct these days. The expense of taking apart and recycling the components is often the cheapest way to deal with the problem. Western firms that specialize in recycling elderly munitions will have a lot less business for the next decade or so and Russia will have fewer spontaneous explosions in munitions storage sites.