HOW TO USE GIBBED SAVE EDITOR *BASIC*

Hey, I had a question: whenever I make certain weapon combinations, such as:

They work perfectly whenever I pull them out of my bank- they do exactly what I want them to. However , if I put them back into the bank, exit the bank menu, then re-enter the bank menu, the extra stats (the extra barrels, etc.) all disappear, and it returns to it's base stats as if I never modded it. What's wrong with it? And why do other weapons modded the EXACT same way NOT do that? Please help!