Philadelphia police officers will be permitted to carry larger-caliber handguns next year, part of a wide-ranging effort that Police Commissioner Charles H. Ramsey is making to upgrade the department's weaponry to match adversaries carrying bigger guns.

Ramsey announced yesterday that officers will have the option to replace their 9mm pistols with more powerful .40- and .45-caliber semiautomatic handguns. The sidearms are produced by Austrian gunmaker Glock.

Though two of four Philadelphia officers killed in the line of duty this year were shot by fugitives carrying powerful guns - one fired an assault rifle - Ramsey was careful not to characterize the decision to upgrade as an escalation.

"We don't want to get into an arms race, and that's not what we're trying to do," Ramsey said. "We're simply trying to make sure that officers have the type of equipment they feel they need to be effective on the street."

But a representative of the Fraternal Order of Police lodge said that officers increasingly feel outgunned and welcomed the opportunity for more firepower.

"As the bad guys get better, we need to level the field," said Mike Trask, a vice president of the police union.

Law-enforcement agencies increasingly are embracing larger-caliber guns. The Pennsylvania State Police now issue .45-caliber Glocks as service weapons. The Los Angeles Police Department has allowed its officers to use .45s for more than three years.

Officers will have to pay for the new guns out of their own pockets - even with a discount, a new Glock .45 costs close to $500. The firearms must conform to the department's specifications, and the officers will need to be trained and certified to use them before they can carry them.

The larger-caliber handguns fire heavier and slower bullets, which experts say are more likely to stop an adversary than smaller rounds. The department uses hollow-point bullets that are designed to expand on impact, reducing the chance of bullets passing through a target and striking bystanders.

"If we can fire one shot from a .40 or a .45 and stop the individual, vs. shooting three or four shots with a 9mm, we would prefer shooting one time only to neutralize the individual," said Capt. Mark Fisher, the department's firearms instructor.

The upgrade in sidearms is the latest move Ramsey has instituted since taking over the department in January to give officers more tools to subdue criminals.

In recent months, the department has deployed 250 new Tasers to officers trained in crisis intervention; the shock-inducing devices previously were only handled by supervisors. And the department is issuing telescoping metal batons that can be carried comfortably on the belt, which officers say make such a startling noise when retracted that individuals sometimes submit without a blow being struck.

And James J. Binns, a lawyer who has raised private funds to buy police motorcycles and memorial plaques, recently raised $30,000 to buy 100 Mossberg 12-gauge shotguns for the force. "We've got to step it up just to stay even," Binns said.

Ramsey said he was also considering acquiring AR-15 semiautomatic rifles - a civilian version of the military M-16 - and training regular patrol officers to use them "should a major incident occur."

"That's just one more effort to try to make sure our department is where it should be in terms of its overall preparedness," he said.

The upgrade to larger-caliber handguns would be the first change in the department's sidearms since Commissioner Willie Williams authorized officers to buy their own semiautomatic Glock 17 and Glock 19 guns in 1989. The Glocks later became standard issue for all Police Academy graduates, though about 600 of the department's 6,700 officers still carry the .38-caliber revolvers, the former service weapon.

Ramsey's order authorizes officers to buy the .40-caliber Glock 22 and Glock 35 models or the .45-caliber Glock 21 or Glock 21-SF.

"What is important is that the officers have a gun they are most comfortable with, that gives them confidence," said Chief Inspector Joseph Sullivan, who as head of the department's training bureau also was responsible for organizing four funerals this year for officers killed in the line of duty.

Two of the officers were killed by gunfire: Sgt. Stephen Liczbinski, who was killed in May by a gunman armed with an SKS assault rifle, and Officer Patrick McDonald, who was killed in September by a felon armed with a .45-caliber pistol.