Shareholder activism drove the biggest gains among US industrial sector stocks in January as railroad CSX (CSX) - Get Report and specialty aluminum fabricator and aerospace firm Arconic(ARNC) - Get Report topped the winners' column.

Solid earnings reports contributed to gains among those rounding out the top 5 while a well-received acquisition lifted the group's final stock.

CSX shares rose 29.1% during the month as the railroad is reportedly in talks with an activist seeking to overhaul it ahead of a key deadline for investors to nominate candidates to the company's board.

Officials from Jacksonville, Fla.-based CSX met with veteran railroad executive Hunter Harrison and representatives from activist Mantle Ridge over the firm's push for more than three seats on the company's board, according to a report in The Wall Street Journal.

Harrison stepped down as CEO of Canadian Pacific CP earlier this month to join Mantle Ridge's efforts to shake up CSX.

The report said that while CSX, which was represented at the meeting by board members Edward Kelly and David Ratcliffe, is open to a compromise it is reluctant to surrender that many board seats. The two sides are trying to reach a compromise before the Feb. 10 deadline for investors to nominate directors, though that date could be pushed back if the company sees a reason to continue talks.

Arconic, the second best first-quarter performer, rose 22.6% in January.
Investors are reportedly pushing for the ouster of Arconic CEO Klaus Kleinfeld, the architect of a series of transactions by Alcoa Corp-Corp to diversify the company away from commodity metals and the subsequent spinoff that created Arconic.

Paul Singer's Elliott Management, an investor in Alcoa before the November split that created Arconic, in recent months has raised its stake in the spinoff from 7.5% to more than 10%, with sources saying that the firm was focusing discussions with management on how to improve margins.

The Wall Street Journal reported Monday that some major Arconic shareholders blame Kleinfeld for the company's poor results of late, noting a history of missed forecasts dating back to before the split.

Elliott already has three board seats at Arconic as part of a standstill agreement reached with Alcoa in early 2016. The report said that the agreement prohibiting further confrontation with the company has ended, allowing for the possibility that the firm will seek additional board seats before Arconic's Feb. 5 nominating deadline.

The third best performing stock, United Rentals(URI) - Get Report , saw its shares add 29.1 % during the quarter, powered by its well-received acquisition of NES Rentals in a cash deal valued at about $965 million.

Chicago-based NES specializes in providing cranes and other aerial equipment to more than 18,000 industrial and nonresidential construction customers. The company, which is majority-owned by private equity firm Diamond Castle Holdings, has 73 branches and about 1,100 employees spread mostly throughout the eastern half of the United States, generating Ebitda of $166 million on sales of $369 million in 2016.

Rockwell Automation(ROK) - Get Report and  W W Grainger(GWW) - Get Report were the fourth and fifth best performers, drawing support from a pair of solid earnings reports and rising 10.1% and 8.8% respectively.

Industrial automation equipment maker Rockwell said its first-quarter sales rose 4% from a year ago to $1.5 billion and that the quarter's net income jumped 15.7% to $214.7 million or $1.65 per diluted share versus last year's $185.5 million or $1.40 per share.

For its part, Grainger reported that sales in the fourth-quarter ending in December rose 2% from a year ago to $10.1 billion.

Net income for the quarter fell 21.2% to $606 million or $9.87 per diluted share compared to the $769 million or $11.58 per share in the same quarter last year. Sales rose 2%.