Warren Buffett's Berkshire Hathaway Inc. said Friday it boosted its stake in cable-television operator Charter Communications Inc., and signaled it may have another large investment planned after agreeing to buy Precision Castparts Corp. in its largest-ever purchase. Berkshire also appeared to have shed its stakes in oilfield-equipment provider National Oilwell Varco Inc. and refiner Phillips 66 in the second quarter, as the oil industry struggles with falling prices.
The changes were disclosed in a U.S. Securities and Exchange Commission filing detailing Berkshire's $107.2 billion U.S. stock portfolio as of June 30.
Berkshire kept some details about its holdings confidential. The SEC sometimes lets the Omaha, Nebraska-based company delay disclosures of new stakes so Buffett can build them quietly, rather than have investors piggyback on him before he finishes.
The filing Friday indicated that only a small percentage of the $3.09 billion of stock that Berkshire bought in the quarter went to companies it already owned.
Berkshire held 8.51 million shares of Charter worth $1.46 billion June 30, up from 5.98 million shares March 31.
It also confirmed its purchase of 20 million shares, or 8.7 percent, of paintmaker Axalta Coating Systems Ltd. from controlling shareholder Carlyle Group LP.
Berkshire reported lower stakes in conglomerate Chicago Bridge & Iron Co., media company Viacom Inc. and Wabco Holdings Inc., which sells braking and suspension systems for commercial vehicles.
It swapped most of what was once a much-larger Phillips 66 stake for a chemicals business in February 2014.
Friday's filing did not disclose who made which Berkshire investments. Smaller investments are frequently made by Todd Combs and Ted Weschler, who may eventually succeed Buffett as chief investment officers.
Combs invested in Precision Castparts before Berkshire said Monday it would buy the aerospace partsmaker. The transaction valued that company at $32.3 billion. Other prominent investors such as Davis Selected Advisers and Jana Partners bought Precision Castparts during the quarter.
Wells Fargo & Co. remained Berkshire's biggest stock holding. Kraft Heinz Co. became Berkshire's second-biggest holding last month, when H.J. Heinz Co. bought Kraft Foods Group Inc. That transformed Berkshire's 52.5 percent stake in Heinz into a 26.9 percent stake in Kraft Heinz.
Berkshire owns more than 80 businesses, including the BNSF railroad, Dairy Queen ice cream and Geico car insurance. Buffett, who turns 85 Aug. 30, has run Berkshire for 50 years.
(Reporting by Jonathan Stempel in New York; Editing by Dan Grebler; editing by James Dalgleish)