Correction: A previous version of this article said that Richard A. Gephardt served as Senate Minority Leader. He served as House Minority Leader. This version has been corrected.

Former U.S. representative Harold L. Volkmer, a Missouri Democrat who was a brusque but effective voice against gun-control measures during his 10 terms in Congress, died April 16 at a nursing home in Hannibal, Mo. He was 80 and had had recent bouts with pneumonia.

After an early career as a prosecutor and state legislator, Rep. Volkmer was elected to the House in 1976 from a northeastern Missouri district that borders the Mississippi River and is widely known as the setting of many Mark Twain novels.

The region earned the nickname “Little Dixie,” reflecting the rural and conservative heritage of early settlers from Kentucky and Virginia. But the district sprawled to more liberal enclaves, such as the university town of Columbia, prompting Rep. Volkmer to balance the needs of a diverse constituency.

Over time, the district became more conservative. Rep. Volkmer’s loss in the 1996 election to a Republican was chalked up to those shifting dynamics as well as his admittedly gruff personality, said David Leuthold, a retired political scientist at the University of Missouri.

Rep. Volkmer was a stalwart advocate for Second Amendment protections and received strong support from the National Rifle Association, on whose board he sat after leaving office.

His signature piece of legislation was the Firearm Owners Protection Act, an influential law that in 1986 weakened many long-standing restrictions on interstate sale of guns and ammunition. The Senate’s co-sponsor, James A. McClure (R-Idaho), died in February.

The firearm bill brought Rep. Volkmer his greatest exposure in a career that was largely out of the national limelight.

His name surfaced in the news in January 1995, when he came to the defense of Rep. Carrie P. Meek (D-Fla.), whose criticism of House Speaker Newt Gingrich’s $4.5 million book advance was struck from the congressional record.

On the House floor, Mr. Volkmer repeated the criticism of Gingrich (R-Ga.) and questioned whether the speaker works for “the American people or his New York publishing company.”

Wielding his considerable knowledge of parliamentary procedure, Rep. Volkmer embraced a new role as an irritant to Republicans, who controlled the House.

He volunteered to serve as a front-line defense against what he considered Republican overreaching on legislation and House procedure.

“He’s enjoying the role of the minority,” then-House Minority Leader Richard A. Gephardt (D-Mo.) told the St. Louis Post-Dispatch. “I’m happy to see him unplugged.”

Harold Lee Volkmer was born in Jefferson City, Mo., on April 4, 1931. He graduated from the University of Missouri law school in 1955 and then spent two years in the Army.

He was prosecuting attorney of Marion County, Mo., which included Hannibal, before serving in the Missouri House of Representatives from 1967 to 1976.

Mr. Volkmer’s first wife, the former Shirley Braskett, died in 1995. Survivors include his wife of 13 years, Dian Sprenger Volkmer of Hannibal; three children from his first marriage, Jerry Volkmer of Farmington, N.M., John Volkmer of Chesapeake, Va., and Beth Volkmer of Fairfax; a brother; four grandchildren; and three great-grandchildren.

Toward the end of his U.S. House career, Rep. Volkmer enjoyed his role as a parliamentary warrior. Even his ideological opposites were impressed by his ability to win, obstruct or delay legislation.

When the sharp-tongued Rep. Robert K. Dornan (R-Calif.) accused President Bill Clinton in 1995 of giving “aid and comfort to the enemy” by avoiding the draft during the Vietnam War, Rep. Volkmer had Dornan’s comments scissored from the congressional record.

According to the Post-Dispatch, Mr. Volkmer later took Dornan aside and advised him on how to make his point without violating a House rule against personal attacks.

“If you know the rules, you’re more apt to be able to have some effect on what goes on in the House,” Mr. Volkmer said.