On the second DLC Map “The Shadowed Throne” in Call of Duty WW2 you can unlock a Pack-a-Punch Machine to upgrade your weapons for more damage. This Pack-a-Punch guide will walk you through the necessary steps:
Step 1: Acquire the Wunderbuss
Follow this guide to learn how to build the Wunderbuss.
Step 2: Uncover the panels of the fuse boxes
Make sure that you take a throwable with you that causes explosive damage, not the throwing knife, flare or the flash grenade (the semtex grenade is the best one for this). You now have to make your way over to the spawn area and then the destroyed building area right next to it. The panel that you have to uncover in the spawn is located behind the bars in the sewer part of the spawn room:
The second and last panel will be in the destroyed building, on the right side when looking at the door that leads to the main street:
Step 3: Charge the fuses
You now have to get the Wunderbuss out and use the primary fire mode ( or ) on both fuse boxes. Charging up one set of fuses will cause the Übersprengen machine to be lowered down and charging up the second set will cause the lift door to open, giving you full access to the Übersprengen. The lift is also located in the destroyed building, basically in the same area as both fuse boxes. Upgrading a weapon will cost you 5000 jolts.