devil dog

A free gunsmith lesson!, yes leade is built on the reamer, but that depends on the reamer used. Now when you do a set-back, you are cutting metal off the chamber side of the barrel were the threads screw into the receiver, one thread is appx. .190, depending on the thread pitch,so now you can fix headspace or an extra long throat to that point, and by turning another thread on the bottom side you can index the barrel with the sights in the correct position. Now you have a short chamber, with a match or a custom reamer, that doesnt have much or any leade, cut the new chamber to a tight S.A.A.M.I. or a custom chamber to your liking without the excesive leade the manufactors build into it to cover their buts "because our country became so SUE crazy".
As far as the Wylde chamber, that is another thing the manufactors use to cover their buts!, due to the fact that there is so much military surplus and it will function in a .223 chamber, the manufactors made the leade in the .223 chamber longerto accomidate the 5.56 in commecial rifles to keep the presures down, but it is still shorter than the 5.56 chamber because most commecial rifles WONT be functioning fully automatic. Armalite, Bushmaster, DPMS and others also have their form of the Wylde chamber that Rock River/Wilson uses.
As far as shortening the leade to accurize a rifle, it does little, mostly it just saves the first portion of the lands and grooves because there isnt as much jump at ignition. That is why I said to just rebarrel, you get much better material and workmanship in a name brand barrel than messing with a stock barrel, but thats not to say you cant get a shooter out of a stock gun.