Detective Constable Will Lander of South Yorkshire Police also believes that the Home Office has "drastically miscalculated" the number of accessories and therefore the cost of the guns surrender. He believes the expected pounds 150m compensation bill could be far higher because of the huge number of unexpected extras, such as holsters and bullet magazines.
With a month left to hand in an estimated 160,000 high-powered revolvers, ammunition and accessories, only about one-quarter are thought to have been collected.
DC Lander, who is helping to organise his force's collection, told Police Review magazine: "Forces had no idea how many reloading components were being kept by the public. A prime example is that we've had half a Transit van full of accessories from a man who had only six pistols. The bill for this is going to be double or triple what the Home Office thinks. The real problem we are finding is with storage. We've had to acquire another room for all the stuff and it's still coming in thick and fast."
Earlier this month the firearms lobby launched legal action against the Government claiming compensation, which could run into hundreds of millions of pounds, for loss of business and amenities.
Under the Firearms Act, which was enacted after the Dunblane school massacre in March last year, when 16 children and their teacher were killed, the estimated 160,000 higher calibre handguns must be surrendered by 30 September. After this date it will be illegal to possess one of the revolvers and law breakers can be jailed for up to 10 years. Legislation to outlaw the estimated 40,000 smaller .22 guns and below is still going through Parliament.
Of 20,000 revolvers expected to be surrendered in the Metropolitan Police area only about 4,700 of the larger-calibre weapons have been handed in, with about 640,000 rounds of ammunition. An additional 1,300 less powerful .22 handguns have been surrendered.
The Home Office has said that compensation, starting at pounds 150 for a standard pistol, will be paid out only after all guns are returned.