Hello shooters! I am looking to purchase a AR-15 rifle that is extremely reliable for both home defense & plinking at targets! I am no beginner to shooting this style of rifle --I shot Colt's M-16 for 3 years while active in the Marine Corp! I need a AR-15 rifle that has a barrel lenght of 18 thru 20 inches long and is extemely resistant to jamming! Thank-You for your thoughts!