Are you invested in gun stocks?

Could banks restrict gun sales?

If you're invested in the stock market via a 401(k) or a stock index fund, you may own shares in a company that manufactures assault weapons, including the AR-15 used in the mass shooting in Parkland, Florida, last week.

"All those index funds that you might have through your 401(k), your broker, whatever -- you actually own gunmakers potentially through these index funds," Rob Cox, Reuters BreakingViews columnist told CBSN in an interview.

Cox pointed out that even owning an fund that tracks the Russell 2000 small-cap index could mean you're invested in companies like Smith & Wesson, owned by American Outdoor Brands (AOBC), or Vista (VSTO), which manufacture various types of guns.

He said investors should first understand what they may own and, if they're uncomfortable with their investments, contact the fund's manager and say, "Look, I'm concerned. I want to make sure that my investments aren't going to support financially companies that make products I don't agree with." 

About 35 percent of U.S. stock mutual funds include investments in a maker or retailer of guns and ammunition, which adds up to more than $17 billion spread across more than 2,000 funds, according to a tally by a nonprofit advocacy group called Goodbye Gun Stocks. The group also classifies retailers that sell firearms -- including Walmart (WMT), Cabela's (CAB) and Dick's Sporting Goods (DKS) -- as gun stocks.