Herndon-based Deltek changed hands between two private equity firms last week, and its new owner plans to take the public company private.

Thoma Bravo’s $1.1 billion deal for Deltek suggests it still sees room to grow the government contracting software specialist, even as federal spending slows.

New Mountain Capital, a private equity firm known in government contracting circles as an investor in Camber and Apptis, initially invested $180 million, which included $75 million in debt, in Deltek in April 2005, according to a Securities and Exchange Commission filing.

In May 2009, New Mountain invested another $46.7 million in the business, which specializes in software and other services geared at contractors and professional services firms.

Now, Thoma Bravo, which is based in Chicago, is set to pay $13 a share — about 7 percent lower than the company’s closing share price the day before the deal was announced. Deltek noted that the price represents a 24 percent premium over its share value on June 11, the day before it sent out confidential sales information to interested parties.

Thoma Bravo declined to comment.

New Mountain, which owns about 40.8 million shares, stands to make about $530.1 million from the deal.

Steven B. Klinsky, New Mountain’s chief executive, said the company stayed with Deltek for longer than is typical.

“You’re under a responsibility to return money back to your investors,” Klinsky said. “We actually held this for seven years because the growth was so good.”

Under new ownership, Deltek’s leadership said the company will be mostly unchanged. It will maintain its executive team and its Herndon headquarters.

“New Mountain Capital has been with us for a very long period of time. They’re the definition of a long-term investor,” said Kevin T. Parker, Deltek’s chief executive who took over shortly after New Mountain bought in. “They weren’t going to be a shareholder forever.”

In recent years, private equity has been drawn to contracting, which produced solid returns even as the rest of the economy weakened.

But as private equity firms consider how to exit their contracting investments, they shouldn’t expect IT services businesses to be valued like Deltek, said Jason F. Rigoli, a managing director at private investment firm Monument Capital Group.

Deltek is “a software company that owns a niche, and it happens to be a niche that is a very, very big market,” he said. For “bread and butter” government contractors, the options may be more narrow.

Going public is simply off the table at the moment for federal contractors, Rigoli added. But private equity owners may look to sell either to other private equity firms or to larger contractors.

Bob Kipps, managing director of the McLean-based investment firm KippsDeSanto, said some private equity firms may end up waiting to sell their investments, particularly if their companies are suffering from government spending cuts.

Deltek grew substantially during New Mountain’s ownership, picking up local companies Input, FedSources and MySBX, among others.

“We’ll continue to do acquisitions, we’ll continue to expand internationally,” Parker said, particularly pointing to Asia and Latin America as potential growth areas.