Im looking to buy a AR-10 in the next few months and would like some opinions. Id like to be able to use it as a HD / Hunting Gun and have a few questions. Would i be able to change uppers to calibers like i can on an AR-15? Would i be able to take the AR-10 Lower and put a AR-15 upper on it? Also right now im looking at DPMS in the 243win and would at a later date get a 308 upper to swap in. Would that be a reliable company to deal with?