7 days notice for anti-social behaviour is the way to go, I think.
Threatening behaviour and talk of shotguns is pretty anti-social I would imagine.
Actually getting him/her out is the tricky part though.
Whilst you will probably be legally entitled to possession of your property actually executing that is messy if your tenant digs his heels in...........and an illegal eviction could result in court looking very crossly at it if your tenant goes to court to seek an order to be reinstated.
I received death threats in a similar situation.....but carried out the eviction anyway and have heard nothing since...