Alright, while I am not sure exactly what model # my AR is due to me buying it from an individual selling it online. I do know it's a rock river, has the mid length gas system and has the quad rail free float handguard on it. My problem is I want to lighten up the front of the gun a bit. The current handguard is the yankee hill aluminum free float. According to YHM's page it weighs 17.5 oz. Would switching to the lightweight aluminum quad rail which weighs 12.4 oz make much of a difference? I've always felt it was heavy, and was reassured that my assumption was correct when my friend who just returned from Iraq held my weapon and thought the front end was very heavy. I see on tv people holding their ar's with one hand quite often, and with apparent ease. Mine strains your arm. Now I know the weapon he is use to is the M4 which has the 14" barrel which will cut down on some weight, and he has a different handguard setup on his. he doesn't have the quad rail. I think he said he's using a surefire lower which has a light built in.. then something else on top. All I know is I want mine to be lighter so it's easier to maneuver. So will shaving 5.1 oz off with a different handguard make a big difference? I don't know anything else to do if I want an aluminum free float and don't want to spend a crap load of money. I just want to make my gun so it isn't a tank, so any suggestions will be greatly appreciated! and btw... I have heard that the YHM freefloat quad rails have had problems in the past.. nobody ever said why but I had just heard that. must have been them moving or something? says they are new and improved now with anti-rotation screws. hopefully that's what the problem was and it's now fixed.