CHARLESTON, W.Va. -- U.S. Sen. Joe Manchin said Wednesday that he was co-sponsoring legislation to expand gun background checks "as a proud gun owner, an NRA [National Rifle Association] member and a law-abiding citizen" -- even though the NRA came out Wednesday against the compromise.Owners of gun stores must currently make sure any customer who buys a weapon has not been "criminally or mentally adjudicated," Manchin, D-W.Va., said during a telephone press conference with West Virginia reporters on Wednesday afternoon.If his legislation passes, Manchin said, "any gun sale at a gun show will also be subject to a criminal and background check, and also if [customers] buy it online. Basically, this closes down loopholes."It's not clear exactly how many gun purchases would be affected by the compromise announced by Manchin and Sen. Patrick Toomey, R-Pa., on Wednesday -- or how many gun purchases and transactions would still be exempt from background checks.In a statement posted on his website Wednesday afternoon, Manchin said the legislation he is co-sponsoring will expand "the existing background check system to cover commercial sales, including sales at gun shows and internet sales."Manchin also believes it will strengthen the "existing instant check system by encouraging states to put all their available records into the National Instant Criminal Background Check System."The legislation, Manchin added, will also create "a National Commission on Mass Violence to study in-depth all the causes of mass violence in our country."The Manchin-Toomey legislation would not restrict personal sales of guns among family members and neighbors."Transfers between family, friends, and neighbors do not require background checks," Manchin's website points out."You can give or sell a gun to your brother, your neighbor, your coworker without a background check. You can post a gun for sale on the cork bulletin board at your church or your job without a background check."During his teleconference, Manchin supported efforts to install protective windows in schools and expressed ongoing concerns about the prevalence of violent video games.The Manchin-Toomey legislation -- focusing on "direct background checks at gun shows, gun stores and online" -- is scheduled to be the first amendment discussed next week, if debate on the pending legislation proceeds in the Senate.Under his proposed legislation, Manchin added, "all internet sales will be treated the same" -- whether made inside or outside the state. "I have talked to many gun dealers in West Virginia," Manchin added. "This bill does not infringe on their rights and it strengthens the right of law-abiding gun owners."Today, there are 50,000 federal firearms licensed dealers in America."People who buy guns at flea markets will also be subjected to background checks," Manchin said. "If an underground ATF [Alcohol, Tobacco and Firearms] agent comes to the show, and guns are sold improperly, that will be a felony."On April 3, Mingo County Sheriff Eugene Crum was shot and killed by Tennis Melvin Maynard, who had a record of mental illnesses.If Maynard had criminal or mental illness records, Manchin said, he should have been prevented from buying a gun. "But it doesn't stop anyone from being a thief," Manchin said on Wednesday. "We all know people who have been mentally challenged. We are doing very little as a society to get them help. Then we have these horrific tragedies. ..."We should be keeping guns from the hands of people who shouldn't have them."Reach Paul J. Nyden at firstname.lastname@example.org or 304-348-5614.