An image of a serial number imprinted on a shell casing.

PROVIDENCE — Sgt. Robert Boehm, Providence police armorer, knelt down and squeezed off four shots from a .40-caliber Smith & Wesson semiautomatic pistol into a special firing chamber set up in the garage of the Public Safety Complex.

As he did so, U.S. Senators Jack Reed and Sheldon Whitehouse, Mayor David N. Cicilline, other officials and news reporters watched with their fingers in their ears for protection against the reverberation.

When the sergeant was done, he fished out of an attached heavy-duty plastic box the shell casings that had been flung free of the pistol when the bullets exploded from those casings. And he handed them off for examination of their distinctive markings by the officials and reporters under a stereomicroscope placed on a table in the auditorium of the building.

The view through the microscope — the illuminated percussion cap on the end of a casing — was shown on a large screen, and inventor Todd Lizotte explained the display.

On view in the demonstration yesterday was what Reed called the “very exciting new technology” of microstamping, which has opened another front in the long-running national political battle over gun control.

The mayor, the senators and Police Chief Dean M. Esserman favor legislation that would require manufacturers of semiautomatic handguns to make their weapons leave unique identifying marks on shell casings — microstamping — that would be used to more easily match a casing with the handgun from which it was expended. That information would be a boon to crime-solving, they said.

Cicilline likened the advantage of microstamping to the police having a suspect’s home address rather than just his partial fingerprints.

“You eventually find the person either way, but one way is a lot easier and faster,” he said at a news conference that included the demonstration.

Massachusetts Sen. Edward Kennedy is preparing legislation for introduction in the Senate that would mandate microstamping and Cicilline announced that he will reintroduce microstamping legislation that failed in the last session of the Rhode Island General Assembly.

California last month enacted a microstamping law and similar legislation is being considered in Massachusetts, Wisconsin and Maryland. The enactment by California, a huge state, heartened microstamping advocates because of its potential ripple effect.

FOR NEARLY a hundred years, firearms examiners have been matching bullets and shell casings to the guns from which they were fired. The tiny burrs randomly left behind in the machining process of making a gun inscribe characteristic scratches and dings on the casings, also called cartridges, that allow conclusive matches to be made.

With established technology, the matching process can be laborious and time-consuming, according to Cicilline and Joshua Horwitz, executive director of the Education Fund to Stop Gun Violence, a nonprofit lobbying organization based in Washington, D.C., who participated in the news conference. And if a casing is not listed in a federal or state government database, no match might be made at all.

What Cicilline, Horwitz and others propose is that manufacturers use lasers to emboss the interiors of their semiautomatic handguns with microscopic letters and numbers that would leave the gun’s serial number, the model and the name of the manufacturer on each casing each time the gun is fired — the process of microstamping devised by Lizotte and co-inventor Orest Ohar. There would be at least three surfaces that would inscribe the casing: the firing pin, the ejector and the breech face.

Those inscriptions would enable law enforcers, using an existing federal government firearms database, to quickly trace shell casings to the maker of the gun that fired the casing and to the person or entity to whom the gun was sold.

Microstamping eliminates the “tea leaf reading” now demanded of firearms examiners who try to match microscopic scratches among casings, Horwitz declared.

When a revolver is fired, the casing stays inside the gun. But when an automatic or semiautomatic weapon is fired, the casing is expended through a port in the weapon and is flung to the shooter’s side or rear. Often, it is the only physical evidence left behind at a crime scene, the police and microstamping advocates point out.

The legislation that Cicilline had introduced in the General Assembly would make handgun manufacturers and dealers civilly liable for selling handguns that lack the microstamping feature and would make it a criminal offense to alter a handgun in an attempt to foil the microstamping.

During the news conference there were several fleeting references to the guncontrol debate, with Reed mentioning that in his 16 years in Congress he “has been pushing back against the gun lobby.” The “gun lobby” has done all it can to thwart access by law-enforcement agencies to information about guns involved in crimes, he charged.

Advocates say that a microstamping law would not restrict gun ownership or access, would not require the creation of another database, and would impose a minimal cost on manufacturers.

gsmith@projo.com