I had some fun with the milling machine yesterday. I sectioned these two 6.5mm bullets. The HP is the superbly accurate PPU 120 grain BTHP, the lead tip is a Hornady 129 grain Interlock. The photo isn't the best, but you can see the relative jacket thicknesses. I noted that the PPU has a slightly thicker base but otherwise, the thicknesses appear to be comparable. What isn't evident in the photo is that the "interlock" feature is the barest of infringement into the core by the jacket. It's almost imperceptible even when the bullet is under magnification. The other thing that isn't evident by any scrutiny is the hardness of the jacket. The Hornady bullet has the much tougher skin as evidenced by the way the mill cut into it. The PPU was much softer.
That said, the PPU will shoot a half-inch from my FN. Maybe it was a bad day for me but my first attempts with the Interlocks ( 47.0 IMR 7828) gave groups that seemed to want to achieve greatness but ended up just over an inch. I write it off to too much jangle juice (caffeine) that morning.~Muir