Updated at 7:40 p.m. ET
Walmart and Dick's Sporting Goods say they won't sell guns to customers under 21, and both are putting new restrictions on ammunition sales.
Dick's Sporting Goods, one of the largest sports retailers in the U.S., has announced it is immediately ending its sales of military-style semi-automatic rifles and is requiring all customers to be older than 21 to buy a firearm at its stores. Additionally, the company no longer will sell high-capacity magazines.