That just depends upon how far you want to jump them. What's your goal? Are you able to accurately measure bullet touching lands? Or are you fixing to buy a new barrel and want to know how to have it chambered?
I started with a standard chamber, then took a dummy round with the bullet set to the length I wanted to a local G.S. and had him throat it for that bullet. But that was because I got the barrel for a steal. If ordering a new barrel, talk to the supplier and see if they'll chamber it to your specs.
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