Re: threading question
Good advise already.
To add to it...
What are you putting on the rifle? Why are you threading the barrel?
Reason I ask is if you are mounting a precision device, like a sound suppressor or some brakes, you should have the host's threads matched to the device. Not all threads are created equal. The geometry of the thread can be different for different items. The length of the thread (called the tenon length) might also be different for different devices.
If you are threading for a future purchase, I suggest you wait until you have the device you want to mount already in hand. Take the rifle and device to your gunsmith for the best fit possible.
Mark