A woman and her two children were tied up and threatened with a sledgehammer before robbers ransacked their home and made off with a number of guns.
Four men burst into the house on Halfpenny Lane in Longridge, near Preston, just after 5.30pm on Tuesday and threatened the woman and her two boys aged eight and 10.
During the robbery the family were threatened with a sledgehammer and tied up with dressing gown cords.
The mother was also punched in the face in front of the two children.
The robbers, who are also believed to have been armed with knives, made off in a white transit van with a number of firearms including a pump action shot-gun, a deer rifle and a foxing rifle as well as ammunition.
The firearms had been in a safe.
They are described as all wearing skull masks and gloves and speaking with Liverpool accents. One also had a snood covering his face.
Det Insp Paddy O’Neill, of Preston Police, said: “This must have been extremely traumatic for the family involved and thankfully they were not seriously hurt.
“The offenders have stolen a number of firearms and ammunition and I am concerned that they could make their way into general circulation and be used for further criminality.
“I would appeal for anyone with any information to get in touch with us as a matter of urgency so that we can try to recover these weapons.”
Anyone with information should call police on 101 quoting log number 0974 of Tuesday, February 11th or Crimestoppers on 0800 555 111.