It always surprises me what excitement is caused by an inert lump of steel and wood just because it is called a "firearm" - incedentally an utterly inaccurate term as most of the guns we carry are shotguns, which by definition are not firearms. Hm, never mind, accuracy is never important in the "security" business, is it?
A gun is no more hazardous an item than a hockey stick, indeed the latter is arguably more dangerous on a plane as is is far more suitable fot close-quarters fighting than a fragile gun which will break on impact if you use it as a club, even if you could retrieve it from an inacccessible baggage hold.
I can only surmise that the percieved "hazard" with guns is in the event that they are mated with ammunition, which is pure double-jeopardy as "security" are there for the specific purpose of preventing that ammo from coming aboard in an accessible manner.
Further, anyone who thinks a long arm, ie a rifle or shotgun is a suitable weapon for interfering with an aeroplane on the inside is not being very serious about interfering with the conduct of a flight.
As we in the UK are no longer permitted to own short barelled weapons under any circumstance (a fine state of democracy, but that's another matter) this all seems to me to be a bit of a storm in a (non existant) shell-case.