A little over 40 years ago, I built my first 7x57 as a casual target rifle. It was built on a 721 Remington action and the Hart barrel was chambered by my mentor, Art Bourne with a reamer he made. He used a separate throater to cut a throat which was 2845 in diameter and just right for the 168 Sierra. It shot great. Later, I barreled a BRNO ZKK 600 and chambered it the same way. It also worked very well. So it was that, when I drew up a reamer for PTG about 7 or eight years ago, I drew it up to duplicate the chambers we cut with Art's reamer. I've used it to cut several chambers including my own Ruger 77 and it still works just fine. GD
