I'd like to get a lightweight AR. Where is the biggest weight savings? There is not much information on weights of various parts and unless I am comparing complete rifles, I'm having a hard time being able to figure out what to choose to keep it light. Often "Lightweight" AR's (BCM, RRA, PSA, etc) are basically a pencil barrel and that's the only modification. Forged/Billet lower versus Polymer lower or upper: Big difference in weight? Carbine system versus midlength system: Savings here? Lightweight handguard (some are very expensive) versus a simple Magpul MOE BTW, I plan to go with just iron sights and maybe a Crimson Trace rail master laser. That'll help the weight, too.