Advice on carbide insert boring bar

[mike-sid]

I need to make a replacement part for a suppressor. (Yes It is registered with the  NFA, and Yes I have an FFL)  From time to time I get asked to do this from a customer, so I finally want to buy a carbide insert boring bar for the task.  I currently have an Ultradex 1/2" x 6" (S08M SCLCR3) that used CCGT type inserts. This tool is too big to make the cut I need.  The part I'm making is .91" in dia  with a .25" hole in the center.  Now I need to boar out a 60 deg taper cut inside making a cone.  I can start by opening up the center hole, but when I get to the inside of the taper my tool is too big.     I'm thinking a 3/8" boring bar might do the trick but there are so many to choose from. Any thoughts?