I'm getting ready for my first civilian rifle/pistol class in August. If something goes down, I don't want to mess around fixing it, I'll just grab my spare. I'm taking two Glock 19's, but I can't decide whether to throw an extra upper in my rifle case or throw an extra AR in the truck. My primary is a almost new registered 6933 with well used BCM 11.5 in upper (favorite rifle). Is there enough chance of a major problem with the lower to justify taking another complete rifle, or just throw a spare upper in my case?