The pensioner, Kenneth Speakman, was beaten and forced to show his attackers where his guns were stored before he was killed.
The killing is bound to add heat to the debate over private possession and storage of firearms after the massacre at Dunblane last March.
The intruders are believed to have escaped with 12 handguns, including a .38 Smith & Wesson and others, although rifles owned by Mr Speakman were left in the house.
An active member of various gun clubs and a regular deer- hunter, Mr Speakman was a respected member of the gun community.
Police believe that he was attacked first at the front door of his house in Ramsgate, Kent, some time between Monday afternoon and Wednesday evening, when his 51-year-old daughter, Penny Russell, came to visit.
Detective Superintendent Nick Biddis, leading the investigation into the killing, said: "This was a dreadful murder of an elderly gentleman who lived alone. It appears he was first beaten near his front door and then taken into various rooms in the house which were searched."
Mr Speakman had held a gun certificate for more than 50 years and kept his gun collection in secure cabinets in accordance with firearms regulations, Det Supt Biddis said.
He added: "This man was killed for his guns. I want these guns back before anyone else is killed. Guns in the hands of incompetents are dangerous, but in the hands of incompetents and criminals they are a dangerous cocktail."
Mr Speakman was a member of the Thanet Pistol and Sporting Gun Club and the Sixth Thanet Rifle Club.
A neighbour, Joan Bax, said: "He used to go off for deer hunting in Scotland and had a lot of trophies and deer heads around the house.
"He was a real gentleman, always smartly dressed and polite. I know he kept all the guns locked up. He was town clerk at the council and was a very respected citizen of Ramsgate."
Forensics experts are searching the large detached Edwardian house where Mr Speakman had lived for more than 40 years.