Yes the wall thickness is very thin at the twist lock groove location as you can see in this photo. Therefore boring a twist lock barrel cant be done from the back.
The freak insert also goes quite a ways from the front into a freak back. About to the position of the bottom external Orings location as shown in this photo.
I have been pondering the possibility of cutting of a twist lock barrel at the position of the bottom Oring. That would eliminate the twist lock grooves and the hole. Then putting the barrel on a lathe and re-threading it externally to Cocker threads. As you can see in this last photo there may be enough left over to do this.
It may not be a quick way to freak bore a twist lock lock barrel and is not very practical for the older mags because then you would need an adapter but ........ theres allot of really awesome barrels out there that could see new life as a Cocker threaded barrel if this mod was possible. They could then be used on the newer Automags and of course on other markers.
Has anyone attempted to change a twist lock barrel to any other thread before ?