
The ability to replenish the Luger can be interesting for the cases when you need to spend ammo for an other effect than using the weapon.
Well for now the only use case is Warning Shot I think but a single Luger P08 can be used to activate the Warning Shot that you cycle with The Book of War a few times. It gives you the possibility to repel the enemies you don't want to fight and the Book of war can also cycle tactics you use for clues (Followed, Kicking the Hornet's Nest, ...). And you even have the possibility to play those tactic events as fast actions with Chuck Fergus.
To have all these cards in the same deck, I think your best (only ?) choice is "Skids" O'Toole who is also interested in using Chuck Fergus on Cheap Shot, Slip Away, Breaking and Entering and Pilfer.