The police department’s push against illegal guns has turned up valuable evidence about the flow of weapons and led to an increase in confiscations versus a year ago, officials said yesterday.

In April, the police formed a new detective unit, the Gun Enhancement Unit, which interviews every suspect arrested for possession of a gun in the city. After becoming fully operational on July 1, the unit has interviewed more than 1,100 suspects, leading to 220 pieces of intelligence that resulted in a new investigation or assisted an ongoing investigation, according to police data.

In addition to creating the unit, Police Commissioner Raymond Kelly brought all the department’s special gun units under the same umbrella — the Gun Suppression Division. The units had been under different commanding officers in two bureaus.

Through September 31, the division has recovered 849 firearms. About 498 firearms were recovered during the same period last year, according to police data. The division has itself made 118 arrests for guns, officials said.

Citywide, the numbers are up as well. Through September 24, the number of gun arrests by all police officers rose to 2,750 for the year versus 2,404 in the 2005 period, a 14.3% increase.

The number of shooting victims has dipped by 2.4% for the year to date, but increased by 8.7% versus the 2001 figure. Likewise, the number of shooting incidents has dropped by 3.4% this year, but is up by the same amount when compared with 2001.

The redoubled efforts by the police department are part of what Mayor Bloomberg has described as his three-pronged approach to stopping illegal guns from entering the city: increased enforcement, vigorous lobbying, and innovative litigation. Last week, the mayor went to Harrisburg, Pa., to pressure legislators to strengthen the state’s gun control laws, and he is expected to make a gun-related announcement in Boston on Thursday.

The mayor has made it the signature goal of his second administration to stem the flow of illegal guns. He began the campaign after the deaths of two police officers in late 2005 and early 2006, Dillon Stewart and Daniel Enchautegui.

Another of Mr. Bloomberg’s gun initiatives is not having the same level of success.

Using evidence collected by private investigators, the city filed 15 lawsuits against out-of-state gun dealers and brought criminal charges against two city gun dealers for improperly selling guns to undercover investigators earlier this year. Seven of the out-of-state gun dealers are contesting the suit, and five have settled, agreeing to give city-appointed special monitors access to their store. Two of the seven contesting the suits are suing the city for defamation of character. The other two gun dealers have not yet announced their decision about the lawsuits.

With the criminal charges against one gun dealer in Queens — Woodhaven Rifle and Pistol Range — dropped to a violation, and charges against a Brooklyn dealer delayed by many months, some observers have said the city has mired itself in expensive and uncertain legal territory.