Looking to buy M4 Upper Receivers? Count on Brownells.com to provide the best selection and prices every day. With 104 M4 Upper Receivers and M4 Upper Receivers & Accessories in stock ranging in price from $58.99 to $2,599.99, you'll find all the best choices available. As the number one online retailer of gun parts and gunsmith tools, we'll provide excellent customer service, great prices, and top-quality merchandise every day. We're so convinced you'll be happy with all our M4 Upper Receivers that we offer a 100% customer satisfaction guarantee. If you're not completely satisfied with your purchase let us know so we can make it right. When you find the M4 Upper Receivers that are right for you, it's easy to place your order online or over the phone at 1-800-741-0015. As always, we're here to help meet all of your needs for gun parts and gunsmith tools, so if you don't find what you're looking for online, drop us a line and let us know.