Faced with the need to dispose of thousands of Cold War era DPICM (Dual Purpose Improved Conventional Munition) 155mm artillery shells (each one carrying 88 bomblets) and a demand for more 155mm practice shells, the U.S. Army came up with a novel and money-saving idea. The DPICM shells would be emptied of their bomblets and filled with high explosives. Not just any high explosives, but the new less sensitive stuff that is less likely to go off by accident. Recycling this way was cheaper than buying new practice shells.
DPICM was all the rage during the Cold War but has gone out of favor because so many bomblets were duds and lie around for years, until civilians accidentally activate them. In theory DPICM is more effective against enemy troops than conventional shells. The bomblets are basically anti-vehicle weapons with a fragmentation effect that kills or injures most people within 6-7 meters (20 feet) of one going off.
In use for over three decades, the DPICM bomblets (also used in cluster bombs) have a dud rate of about one percent. That means one percent do not explode when they hit something (after being expelled from the shell, before the shell hits the ground). These duds can explode later if picked up or stepped on. That's a lower dud rate than for most munitions but one shell carries 88 separate small bombs, while each MLRS DPICM rocket carries 644. Earlier versions of these bomblets had even higher dud rates. So you have a lot more dud munitions sitting around on the battlefield, ready to injure your own troops and civilians.
DPICM continues to be used because the bomblets more than triple the effectiveness of each conventional shell (which is just filled with an explosive charge). The U.S. has stopped using DPICM and instead switched to even more effective GPS guided high-explosive shells. The huge quantities of DPICM shells bought during the Cold War as a war reserve (to supply heavy fighting for at least 30 days) are reaching the end of their shelf life and have to be disposed of. Normally this means extracting the explosives (which are now less stable and effective) and rendering the stuff harmless while selling the metal and electronic components for scrap. Instead, the Cold War super shells will be recycled into training ammo.