Having fun cheating with the reload-shot mechanic ;), please don't fix. Not sure if the upgrades are working, i drag them to the gun or crafting slots but nothing happnes(they dont 'stick' to the slots)
Oh, upgrading does work. You start dragging the upgrade, the slots turn white if they can accept them, you drag them over, your mouse cursor changes and a green arrow appears showing where the upgrade will be positioned, and then you drop it.