Have a few of these brand new Colt sling bags to hold an AR. Has Molle and a fully adjustable interior to adjust to your specific rifle. Here is a snip of the manufacturer info.
"Now you can carry your modern sporting rifle and pistol at the same time. Unique messenger-style bag holds your rifle on your back and your pistol on your chest in a quick access pocket. Padded liner cushions heavy loads and moisture-wicking body-side materials keep you dry and cool. High-visibility lined exterior pocket for increased visibility in low-light conditions."
"Now you can carry your modern sporting rifle and pistol at the same time. Unique messenger-style bag holds your rifle on your back and your pistol on your chest in a quick access pocket. Padded liner cushions heavy loads and moisture-wicking body-side materials keep you dry and cool. High-visibility lined exterior pocket for increased visibility in low-light conditions."