Warren Buffett's Berkshire Hathaway has plowed $150 million into Liberty SiriusXM, and looks set to invest another $180 million

• Warren Buffett's Berkshire Hathaway looks set to invest more than $330 million into Liberty SiriusXM in a matter of weeks.
• The billionaire investor's company spent $152 million on the media group's "C" shares between May 21 and June 1, SEC filings show.
• Berkshire also received 4.3 million rights to buy more "C" shares as part of a rights issue, and purchased another 2.9 million rights on the open market last month.
• Exercising all of its rights would cost about $182 million and boost its stake to around 43 million "C" shares.
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Warren Buffett's Berkshire Hathaway has plowed more than $150 million into Liberty SiriusXM in the past two weeks, and appears poised to invest another $180 million on top of that.

The famed investor's company spent $152 million to buy 4.8 million of the media group's "C" shares between May 21 and June 1, raising its stake from roughly 30.9 million shares to 35.7 million shares, SEC filings show. The position is worth about $1.4 billion at the current share price.

Berkshire also held 14.9 million of Liberty SiriusXM's "A" shares at last count, valued at $574 million based on their closing price on Wednesday.

Buffett's company looks set to buy more shares on the cheap and bolster its holdings significantly.

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Buying at a bargain

Liberty Media divides its business interests in three groups, each with an associated stock: Liberty SiriusXM, which owns most of satellite-radio giant SiriusXM and parts of Live Nation and IHeartMedia; Braves, which owns the Atlanta Braves baseball team; and Formula One, which owns the motorsports business.

The media titan recently reallocated assets between the groups, resulting in Liberty SiriusXM owing $750 million to Formula One. It launched a rights issue — where a company issues shares and offers them at a discount to its shareholders — last month to raise cash to repay the loan.

Berkshire's shareholding meant it received 4.3 million rights. It can exercise each one to buy one "C" share for $25.47, representing a discount of about a third to the current stock price. If it doesn't use them, its stake in Liberty SiriusXM would be diluted by the new shares issued.

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Spotting a bargain, Berkshire shelled out about $27 million to buy another 2.9 million rights on the public market in the second half of May, raising its total number of rights to about 7.2 million. It has until the rights issue expires tomorrow to use them, assuming the deadline isn't extended.

If Berkshire exercises all of its rights at the offered price, it would spend about $182 million and increase its total "C" shares to about 43 million — more than 18% of the outstanding "C" shares expected after the rights issue.

Between its recent stock purchases and potential exercising of rights, Buffett's company could end up investing more than $330 million into Liberty SiriusXM in a matter of weeks.