I'm thinking of changing the barrel and bcg on a non milspec ar to milspec parts. Will I have to take the barrel and bcg to a smith to have the headspace set the same as a bolt gun?
I switched out an Oly arms carry handle to a YHM flat-top. Only thing that didn't fit at first were the pivot holes. Fitting any good or really good finished AR barrel should be done with a torque wrench while following the specs off either the Marine Corps or US Army armorer's manual. Mine shot fine and I am by no means a gunsmith or armorer. I just read the directions and follow them to a "T". Which brands you looking at for the changeover?
Critical dimensions for headspace are well established and known to all makers of 5.56/223 AR-15s. Headspace is accomplished when the barrel extension is pinned in place. If you purchase a barrel and bolt from a reputable manufacturer, it will come correctly headspaced.
If you want extra peace-of-mind, purchase a field gage
A YHM,DSA,etc upper receiver assembled with the small parts is about $125.
I guess if I was buying a whole BCG,and a barrel.I'd be thinking about building a complete upper,and leaving the original upper intact
