Bob Millstone and his team at private equity firm Millstone Capital Advisors have launched a second fund aimed at investing in or acquiring middle-market companies.

Millstone already has raised more than $6 million of a planned $30 million offering for FSM Fund II LP, according to a filing with the Securities and Exchange Commission.

Millstone, citing SEC rules that prohibit disclosure during a private equity raise, declined to comment on the raise. He did say the fund would carry the same investment strategy as the firm’s first FSM fund (launched in 2013) that sought to invest in profitable emerging growth companies with revenue ranging from approximately $10 million to $100 million.

The new raise also lists other Millstone principals, including senior partner Fred Flegel and partner Toby Warticovschi as executive officers.

The firm used its first fund — a planned $30 million offering — to buy restaurant chain Lion’s Choice in 2013 and print and production company The Printing Source in 2014. Millstone declined to discuss the first fund or the amount of its investments in Lion’s Choice and The Printing Source.

Private equity investments reached record highs last year in the U.S. at $2.28 trillion in mergers and acquisitions, according to Dealogic, which analyzes M&A activity, with the middle market accounting for most buyouts.

According to Pitchbook, through the first three quarters of 2015, mid-market private equity totaled $253 billion spread over 1,439 deals — for the full year of 2014, private equity totaled $411 billion over nearly 2,000 deals.

Millstone was previously CEO of construction firm Millstone Bangert several years before it merged with Maryland Heights-based road building services firm Fred Weber Inc., to form Millstone Weber, which has estimated revenue of $190 million.

Bob Millstone’s other venture, Millstone Co., owns the Fountain Lakes Commerce Center in St. Charles, a 2.5 million-square-foot commercial, industrial and retail development. The site has an additional 1.5 million square feet of developable space.