When switching missions on Attack On Teufort, if you remain on the same map, you will keep all weapon/sentry (not canteen or body/class) upgrades. This means that someone can go on 666 Nightmare, spend 5000 worth on their weapons, then switch to an easier mission while still keeping their 5000 dollars of upgrades.
Replication:
- Upgrade your weapons with whatever money you wish
- Switch mission, while staying on the same map
- Enjoy having overupgraded weapons
Points of potential notes:
-refunding upgrades will remove all these upgrades while not refunding any money.