McKenna Long & Aldridge, the Atlanta-based law firm with the oldest and largest government contracts practice in the District, finalized its merger Tuesday with San Diego-based Luce, Forward, Hamilton & Scripps.

The combination lands McKenna Long & Aldridge a spot in the top 100 biggest U.S. law firms, with 575 attorneys and public policy advisers in 11 cities. The move also significantly boosts the firm’s presence in California, nearly doubling its manpower from 124 to 247 attorneys.

The merger, formally announced in January, was in the works since last fall. In Washington, McKenna Long is best known for its government contracts group, which has about 70 attorneys represents the five largest defense contractors based on total contracting dollars in 2011. Luce Forward’s stronghold in West Coast industries like securities and aerospace make it a good fit for McKenna Long, said Luce Forward Managing Partner Kurt Kicklighter, now executive partner at McKenna Long for California.

Luce Forward had six offices and 123 lawyers in California, with large real estate and litigation practices. In 2011, the 138-year-old firm saw gross revenue and profits per partner slide nearly 18 percent and 21 percent, respectively, according to annual figures the firm submitted to The American Lawyer. Kicklighter said the drop-off was “a decline back to the norm,” after 2010 saw unusually high payoffs in large contingency and class action cases.

During the same period, McKenna Long saw revenue and profits per partner grow 4 percent and 1 percent, respectively.

Luce Forward had been frustrated with its failure to grow over the last three years, which was driving force behind the merger.

“I was elected to grow this firm into a larger regional firm,” Kicklighter said. “Instead, we were not successful in adding laterals or growing. We shrunk ... Part of the reason to join with McKenna Long is law firms can’t sustain continued shrinkage if you want to ensure quality to clients.”

Nine Luce Forward partners departed amid merger talks to Jones Day, Pillsbury Winthrop Shaw Pittman and San Diego firm Procopio Cory Hargreaves & Savitch.

Kicklighter said the firm is not anticipating attorney layoffs, but declined to comment on staff redundancies.

McKenna Long Chairman Jeff Haidet was not available to comment Tuesday, but said in a statement that the merger “is about creating more value for our clients through an expanded network of attorneys.”