My AR-15 is set up as a 24" SS varmint freefloater with a very high powered scope. This setup is incredibly accurate and fun to shoot tight groups and work on long range skills, but some times you just want to unload some milsurp ammo! I obviosly am not going to do this with my precious match barrel and I have seen some fairly inexpensive upper assemblies in the Shotgun News (260 range for shorty upper). Are these junk? Can you do any damage to the lower or bolt by switching around or should I be satisfied with unloading 50 rounders in my fold stock 10\22