Only 70% of weapons make it to the battlefield.
the rest is on the blackmarket.
Its quite difficult to blackmarket howitzers and 155mm ammo.
Not a lot of people want these things. Those that have a use for them have them already. Those that would like them can’t, because they are very hard to sneak around and hide. Anyway, the only significant customer for this stuff at the moment is ... Ukraine.
That 70% came out of someines posterior.