BOSTON -- Are there guns in your investment portfolio? It’s an issue that some politicians and gun-control advocates are raising after recent mass shootings prompted calls for tougher laws.

Chicago Mayor Rahm Emanuel wrote letters to six mutual fund companies asking them to sell their stock in gun manufacturers Smith & Wesson and Sturm, Ruger & Co. It’s a critical concern in Chicago, where more than 500 people were murdered last year.

Fund companies should “send a clear and unambiguous message to the entire gun industry that investors will no longer support companies that profit from gun violence,” Emanuel wrote in his letters last week.

Other city leaders, including those in Los Angeles and Philadelphia, are considering similar steps with their pension funds.

Gun control is the kind of issue that can wake investors up to the fact that money in a fund portfolio or 401(k) affects more than just their retirement security. The financial markets support all kinds of companies, including many that an investor may believe aren’t contributing to the greater good.

But whatever one thinks about gun control, removing such an investment from a portfolio on moral grounds isn’t always a simple matter. There are potential costs from putting your principles before profits.

Recognize that over the last 10 years Smith & Wesson has posted an average annualized return of 17 percent, compared with the 8 percent return of the broader market. Similarly, Sturm Ruger, the largest publicly traded gun company, has returned an annualized 23 percent over that time. The vast majority of gun manufacturers are privately held.

LEGAL HURDLES

There would be other potential costs if fund companies or 401(k) managers were to sell gun maker stocks in response to the recent controversy. These companies have obligations to serve the financial interests of vast numbers of individual fund shareholders and plan participants with varying opinions about guns.

For employers sponsoring 401(k) plans, their hands can be tied unless the plan established a mandate to avoid investing in gun makers, says Kathleen McBride, founder of consulting firm FiduciaryPath.

She advises financial professionals who are fiduciaries, a legal designation requiring them to act in the best financial interests of their clients. That obligation is a chief concern cited by Vanguard, among the six fund companies that Emanuel is pressuring. A Vanguard spokeswoman said mutual funds “are not optimal agents to address social change.”

A spokesman for American Funds, which also received a letter from Emanuel, said: “If social issues may have an effect on the investment potential of a company, we take those issues into account as part of the investment process.”

For example, a stock fund manager might expect that gun laws are likely to become more restrictive. That would cut into industry sales, leading the manager to conclude that stocks of gun makers are bad long-term investments. Such a fund manager could justify selling such stocks as beneficial for shareholders. But the manager wouldn’t be justified in selling simply because of moral objections.

INDEX FUNDS

Making changes only gets more complicated with low-cost index funds, which own all the stocks in a given market index.

If such a fund doesn’t track the index closely, then it ceases to be an index fund — no matter whether some of the stocks may be viewed as morally objectionable by some investors.