Well there is nothing wrong with the upper, i am just want another configuration upper the upper i am going to take off is a 20" wilson 1:9 twist that is a flat top and has a gas block on it and a free floating hand guard and a scope. i am wanting to get a 16" heavy barrel not bull barrel with a a2 upper,i can get this upper less bolt and carrier and chargeing handle for 305.00 ,the bolt and carrier and chargeing handle is a extra 140 dollers Y BUY it if i have 1 in the upper i already have