Thanks for the very informative thread.
I didn't realized that M14 had such a beefy bull barrel (if I can say that). Is it particular to 4" M14?
And how about the frame of the 2" M15? Some author (Jinks or Supica) writes that it differs from the normal 4" M15. As you can see on the pic, the topstrap is straight, without any step. It's neither a M14/M19 frame, nor a M15's...
L.