Following the tragic shooting at at Marjory Stoneman Douglas High School in Parkland, Florida, last month, investors became increasingly vocal about funds and other investment vehicles owning shares of publicly traded civilian firearms manufacturers. Even some passively managed exchange-traded funds (ETFs) have come under scrutiny for small stakes in gun makers.

BlackRock, Inc.'s (BLK) iShares unit, the world's largest ETF issuer, is actively informing investors regarding the asset manager's exposure to firearms makers in both its actively managed mutual funds and passive products such as ETFs. American Outdoor Brands Corporation (AOBC), Vista Outdoor Inc. (VSTO) and Sturm, Ruger & Company, Inc. (RGR) are not held in any BlackRock active funds. In BlackRock's "index equity products (where stocks are determined by third-party index providers) – these three companies represent 0.01% of total assets," according to a statement issued by the asset manager. (See also: Sen. Warren Asks Fidelity, Other Funds to Demand Gun Industry Change.)

BlackRock said that 95% of its U.S.-listed ETFs do not hold those three gun stocks. The list of iShares ETFs that do hold shares of civilian gun manufacturers does, however, include some well-known ETFs. That list includes fixed income and equity products. As of Feb. 26, iShares ETFs holding gun stocks included the iShares MSCI ACWI Low Carbon Target ETF (CRBN), iShares MSCI EAFE ETF (EFA) and iShares Core S&P Small-Cap ETF (IJR).

The issuer's ETFs that do not own civilian gun manufacturers also include well-known fare such as the iShares MSCI Emerging Markets ETF (EEM), iShares MSCI KLD 400 Social ETF (DSI) and iShares Core High Dividend ETF (HDV). "For context, 95% of U.S. iShares ETFs do not hold shares of the three publicly traded companies in the U.S. whose primary business is firearms manufacturing: American Outdoor Brands Sturm, Ruger & Co. Inc. and Vista Outdoor. (BlackRock; MSCI, Feb. 26)," said BlackRock. (For more, see: Industries That Could Benefit From Stricter Gun Control Laws.)

Most ETFs are passive products, following benchmarks provided by third-party index providers, such as FTSE Russell, MSCI and Standard & Poor's. Index providers, not ETF issuers, determine the stocks residing in various benchmarks. "Because the companies in an index are determined by third-party index providers, when a client chooses an index that includes a firearms manufacturer, we are unable to sell those shares regardless of our view of the company," said BlackRock.

BlackRock said it has been engaging publicly traded civilian gun makers and that it has had "constructive dialogue" with some of those firms. The fund giant is also engaging retailers, asking those companies, among other questions, how much of their revenue and profit are derived from firearms sales. (For additional reading, check out: All About the Gun Business in America.)