PA is a DeFacto legal OC state, meaning there is no law against it so it is legal. a 'man with a gun' call does not warrant a stop, search, and to be detained. unless the police have R.A.S that a crime is currently, about to or has been commited, then they can't detain you for doing nothing illegal.
read Commonwealth v. Hawkins
taken from above:
The Commonwealth takes the radical position that police have a duty to
stop and frisk when they receive information from any source that a suspect has
a gun. Since it is not illegal to carry a licensed gun in Pennsylvania,4 it is
difficult to see where this shocking idea originates, notwithstanding the
Commonwealth's fanciful and histrionic references to maniacs who may spray
schoolyards with gunfire and assassins of public figures who may otherwise go
undetected. Even if the Constitution of Pennsylvania would permit such
invasive police activity as the Commonwealth proposes -- which it does not --
such activity seems more likely to endanger than to protect the public.
Unnecessary police intervention, by definition, produces the possibility of
conflict where none need exist.