I saw a couple of guys use collapsible laundry baskets during an AR15 match at my local range. Just stand it on it's side, less than $5, and collapses down for easy storage. Works great.
Mainstays Mesh Pop-up Laundry Basket 21" x 13" x 15.5", White - Walmart.com
Arrives by tomorrow Buy Mainstays Mesh Pop-up Laundry Basket 21" x 13" x 15.5", White at Walmart.com
www.walmart.com