How can i take out mementos out of old guns?

[lElysiuM]

years ago i put the trials memento ornament on a ugly ass rocketlauncher no one uses anymore, now i want the momento on my new midnight coup, is that somehow possible? i cant figure out how i can put a memento on it

[Eriana]

no you can not

[Ex]

They seem to be infinite use for me idk.