My solution is probably for a second shorter barreled & lighter rifle with the lower modified to match the lower that is on my 24 inch bull barrel rifle. My own efforts to locate a second upper indicate that for an additional very small cost difference I can have the benefit of all those spare parts that comprise a functional lower. If anything ever breaks or wears excessively, I will be able to use either lower with either upper as needed while parts are on order or repairs are being done.
