I recently purchased the new 5.11 Tactical M4 Covrt Carry Backpack, on sale for less than $100. It arrived today and I have to say I am very pleased with it. The material is good and the stitching and zippers seem well done. Its a sling pack type style with two front pockets. The top pocket has some Molle and velcro type loops that will hold I am sure a small cleaning kit or other type sized little pouch for organization. The second pocket on the front is nice sized and can hold a 32oz bottle and a chest rig and still have a little room. The main compartment will hold a pistol type AR/AK with no problem and will accomadate a up to a 14.5" M4 without much problem. The pictures below show a 7.5 pistol with a Spikes STAB muzzle break, a 10.5" Noveske SBR with an attached AAC M42K suppressor. It will not hold a 12" SBR with a can but without a can a 12-14" SBR should be fine. Below are some pictures for reference.
Front of Pack showing two pockets:
Back of pack showing sling strap and "stablization cross strap":
Top Pocket:
Bottom Pocket empty:
Bottom Pocket with Chest Rig:
Inside with 7.5 pistol AR with Spikes STAB break:
Inside with 10.5 SBR with AAC M42K Suppressor attached (Perfect Fit):
12" SBR with Can = To Long