"Hobo" wrote in message
...

Has there ever been an aircraft with a gun permanently aligned
off-center?

Yes, several going as far back at least as far as WWI.
I'm afraid I'm brain locking on the designations though. In
Vietnam B-57 had gun packs fitted that shot down at a very
sharp angle- may even have been vertical- for night straffing
the trail.

I don't mean swivel mounted, but permanently fixed at a
point other than straight ahead.

Wouldn't a gun pointed at a downward angle make ground attack easier?

I don't know why the idea keeps failing to catch on; it could
be it's too single purpose for fighters or just not as easy to
aim.