The new barreled are 100% made inside the wall of the Proof Research facility.
The old one and a few years ago had Bartlien, Krieger, and Satern barrel liners and had then been carbon wrapped by ABS. This was before Proof Research owned the patents. And the 1st year or so of Proof Research. The new ones are better then the older ones. New advances in carbon wrapping and barrel liner contouring. The older barrels will say the manufacture of he barrel liner on the end cap( Krieger,Bartlien, Saturn).
Brian