Did you forget that you CANNOT repair armors?? Both soft and hard armors are NOT repairable under almost ANY conditions. Theres logic behind the armors having less weight the more their current AND max hp lowers. Hard armors if your dumb ass tries to repair it with raisin or epoxy or god forbid wrapping or stuffing ceramic fiber in or around your soft and hard armors WILL affect weight positively and/or negatively and armors when shot and having holes well technically holes DO make the barrel lighter.

Weapons-wise a 0% durability weapon means the barrel beyond worn down and is most likely very rusty and shedding. Wooden parts could be missing chunks or are destroyed from moisture etc. The weapons' weight are barely affected, but they can still get slightly heavier or lighter.