Seems like you might need these links.
This provides a good sample form and instructions for filing a motion to return in Philadelphia under rule 588.
http://www.courts.phila.gov/pdf/forms/criminal/01-206-Return-of-Property.pdf
This is Rule 588.
http://www.pacode.com/secure/data/234/chapter5/s588.html
And this is from the Victim’s Right Statute.
http://law.lclark.edu/live/files/4976-pennsylvania
(g) Return of property. The appropriate law enforcement agency shall return to the victim property
seized as evidence if the prosecutor’s office determines that the evidence is no longer needed for
prosecution.
(fn 1: 18 P.S. § 11.201)
It’s possible that they will try to hang on to the gun until forced to return it.
Thank you for the links. One would think the victims advocates office would have sent me something similar in their letter,