Standardization/reciprocity/simplification between all states is ideal but not going to become reality and the result will be continued and complicated legal webs, especially when an incident occurs.
Isn't it interesting that the state of Bernie Sanders has the most lax firearms laws in the union; anyone 18 or above (that is not a felon, has a record, etc,) can carry open or concealed with no permit or application including minors with parents consent. Lived in that state in 2016 then took an eight minute ferry ride across Lake Champlain and domiciled in NY where I visited a gun shop with a firearm I had owned for thirty seven years along with an active CC permit from the state of Georgia. While having the piece appraised was asked if I had a permit for it? "What"?! was my only response.
Come to find out, a piece I legally owned for half a lifetime along with the squeaky clean background check for the CC from another state meant nothing to NY; I was required to have a permit for that specific piece issued by NY while in the state of NY! Recognizing my complete (and innocent) ignorance the lady handed the piece back and suggested I leave the store immediately and explained I was fortunate to have visited their "Mom & Pop" operation for it was standard practice for other gun stores to call the authorities hence the piece would be confiscated an myself jailed. My domicile in New York state was brief.