To make his case, Gabelli pointed to GenCorp's $550 million deal to buy Pratt & Whitney Rocketdyne from United Technologies. "They bought Rocketdyne and they're closing on that. And that business — the basic manufacturing business, which has short term hiccups — will earn about 70 cents in three or four years."
GenCorp also has "significant acreage" in the Sacramento, Calif.-area and "real estate is booming," he said.
(Read More: CNBC's Stock Blog)
The second stock that Gabelli expects to double is Legg Mason.
On Monday, Gabelli announced that his firm increased its stake in the global asset management company to 5 percent.
A major reason for his faith in shares of Legg Mason: "[They're] buying back their stock. They had 164 million shares outstanding, they're down to 128," giving it about a $3.6 billion market cap. "They [also] announced that two thirds of their cash flow is going to buy back stock."
Gabelli added, "They're in the investment business, great cash generator, and they're solving a lot of their issues."
—By CNBC's Matthew J. Belvedere; Follow him on Twitter
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