INSTEAD of the Keystone State, you could call Pennsylvania the "Keep Your Head Down State."

And Delaware? "Definitely Not First."

A national report released Sunday knocked Pennsylvania and Delaware as two of just 10 states that failed to report any mental-health records to the National Instant Criminal Background Check System (NICS). New Jersey didn't do much better: In a state with 8.7 million people, just eight mental-health records were submitted through August last year.

Compare that with California, which bested everyone by reporting 256,106 during the same period, according to the study.

Mayors Against Illegal Guns, which released the report, contends that although reporting is voluntary, increased participation in the database is necessary to keep guns out of the hands of potentially dangerous people.

"We're just trying to keep our cities safe," Tom McMahon, mayor of Reading and the group's Pennsylvania coordinator, told the Daily News yesterday. "It strikes me as absolutely astounding that people don't rise up on this and say enough is enough."

The group tackled the issue after, police said, Jared Loughner shot 19 people, killing six, in an unsuccessful effort to assassinate U.S. Rep. Gabrielle Giffords during a community meeting Jan. 8 in Tucson, Ariz.

Under federal law, Loughner shouldn't have been armed.

Loughner bought two guns and passed a background check less than a year after the Army rejected him in 2008 for habitual drug use. But federal law forbids certain people from buying or having guns, including drug users, felons, illegal residents and anyone adjudicated as a mental defective or committed to a mental institution.

Federal authorities tried to increase NICS reporting in 2007, after Seung-Hui Cho went on a shooting rampage at Virginia Tech, killing 32 people. The 23-year-old undergraduate had a documented history of mental problems dating from middle school but still was able to buy two guns and piles of ammunition.

Under the NICS Improvement Amendments Act of 2007, Congress created incentives for states to improve reporting to NICS. But in the past two years, lawmakers have appropriated only about 5 percent of the amount the act authorized in grants to states to improve reporting, according to Mayors Against Illegal Guns.

Consequently, the group's study shows wide disparities in states' compliance.

Other states that reported no mental-health records were Alaska, Hawaii, Idaho, Massachusetts, Minnesota, New Mexico, North Dakota and Rhode Island. Altogether, 28 states submitted fewer than 100 mental-health records to NICS, according to the report.

Some states, like Pennsylvania, maintain statewide databases with such records. The problem with such a system, according to the mayors' group, is that state databases aren't universally accessible, enabling a person with a problematic background to buy weapons in other states.

Besides California, states submitting the most records to NICS, per capita, were Virginia, Michigan, New York, Washington and Colorado, according to the study.

The total "Mental Defective/Committed" count on NICS, as of Dec. 31, was more than 1.1 million records, according to the FBI. But the General Accounting Office estimates that an additional 1.5 million disqualifying mental-health records are still missing from the database.

Loughner's rampage proves "the system is still broken," said Peter Read, whose daughter Mary was slain in the Virginia Tech massacre.