This is the rifle Will tuned a month or so ago as a .357 . Several years ago he machined a 28 inch .250 TJ liner for me for this rifle . Both of my other 25 calibers are in need of work so I put the barrel back on this rile since I have three 201's . The groove diameter is .250 . The bullets were sized to .2505 and tested 10 bhn today . Chonied it today and again I am happy with the numbers .Marvin