HARRISBURG -- The state's computerized background check system will be shut down for an upgrade starting Sunday, despite the outcry from sportsmen and gun dealers who say the timing will interfere with last-minute firearms sales during the start of dove and Canada goose hunting season.

The governor announced yesterday that the state will stick to its plan to begin upgrading the Pennsylvania Instant Check System Sunday evening; however, the work will be completed by 6 p.m. next Wednesday instead of noon on Sept. 6, as originally scheduled.

Dealers, who use the system to conduct instant criminal background checks of gun buyers, have said they will lose sales.

An ad hoc committee of sportsmen and lawmakers met Monday and recommended postponing the upgrade until late September or after Christmas. Mr. Rendell said those options conflicted with other scheduled computer system upgrades or would have added significant cost.

"It is clear that there will never be an ideal time to temporarily shut down the system so we can make changes necessary to ensure the system continues to be safe and useful," he said.

One group of 26 gun dealers, including George Romanoff, owner of Ace Sporting Goods in Washington, Pa., is looking to Commonwealth Court to block the temporary shutdown. Their case is scheduled for a hearing in Harrisburg Friday morning.

"We're miffed," Mr. Romanoff said.

"This is the only system I've ever heard of that has to go down for a three- or four-day period to do an upgrade," he said. "To deprive people of commerce for that period of time is unconscionable."

The upgrade should be done in spurts during evening and early morning hours when gun shops are closed, Mr. Romanoff said.

Col. Jeffrey B. Miller, commissioner of the state police, says the changeover to a new database must be done all at once.

Mr. Romanoff said there must be another way.

"We're all in favor of having the system upgraded for it to run smoother, but it shouldn't have to be this much of an inconvenience, not only to the firearms dealers, but to our customers," he said. "There should have been better planning."

Instant Check is based on 1981 technology and needs to be upgraded to improve its capacity and efficiency, Col. Miller told reporters Monday. The upgrade involves moving 47 million records from one database to another, he said.

Instant Check is used by gun dealers, state courts, the state Department of Corrections, the National Crime Information Center, U.S. Immigration and Customs Enforcement, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, the Pennsylvania Megan's Law Registry and other agencies.