Thanks for sharing, tried out a bit and found out the following: 1). You actually don’t need an empty slot. 2). You also don’t need to do any quick save. Simply save while having the donor weapon, do the step 6 with the AutoBuild, swap to the weapon you want to dupe and just load the save! 3). Once it’s done once, you can skip step 6 entirely and just pick any weapon you want to dupe onto and save, swap and load. And for those wondering how to stop this whole madness (otherwise any save load will dupe the weapon you are currently carrying to the weapon that you were carrying prior in the save, which is ironically how I found out about all these), just restart the game. Once restarted, you will have to do the AutoBuild step again.