On their current mission, my players will come across the aftermath of a Grey Knight purge of a daemonic incursion. One of the clues to what happened will be bolt casings everywhere, including some that are larger than others, made from silver, and etched with venerations of the Emperor. If I know my players, they will want to keep these, probably to sell.
Then I got to thinking: given the fact that Psicannon shells are impregnated with the aura of the Emperor, the spent shell casings may have some kind of game effect over and above their monetary value (I know that's not in the Rule As Written, which is why I'm not posting this in the Rules Questions section; I'm asking about 'fluff' interpretation). The only game effect that I can think of for them that doesn't blatantly turn them into 'magic items' is to count them as Lucky Charms- possibly limited to functioning against Daemons and Psychic Powers.
Can anyone think of a more 'colourful' use than that, which doesn't make them overpowered?