I decided it was time to get serious about long range shooting / hunting so I am ordering a new barrel for my rifle. I have never had a custom rifle or barrel before so this is all new to me. It will be chambered in 300 Rem Ultra Mag. I want a custom throat cut for Nosler 200gr. AccuBond bullets. This is where I need help from the experts here. How do I go about determining the length of the throat to be cut? First I want to build the cartridge then have the throat cut to it. I always used factory guns so I had to tailor the cartridge to fit the gun. From what I read, I am supposed to seat the bullet with the bearing surface to the shoulder neck junction. BobbyL said in another thread “When i set one up i use a case and seat the bullet so the pressure ring is just starting to enter the neck. This gives us the best accuracy and allows for the most FPS by using more powder. The more room in the case the less the pressure will build with a specific charge. This has to be done carefully or you wont have enough bullet left in the neck to shoot it. Yes you want the gas ring or the boattail bearing surface junction right at or up in the neck of the case above the neck shoulder intersect” With that in mind I used a Hornady bullet comparator to measure the bullet. I also emailed Nosler to get the exact dimensions of the bullet. I got two different set of numbers. I got base to ogive .848” and Nosler quoted me .770” Boat tail length I got .093” and Nosler quoted me .110” The neck of the case is .306” I measured the comparator insert and it measured .294” Could that .006” be throwing me off that much? So back to the throat. Using my measured numbers and a .030” jump to lands .848 - .093 - .306 + .030 = .479 throat. Using Nosler’s numbers .770 - .110 - .306 +.030 = .384” I already changed the throat three times. I think I may have wore out my welcome. Luckily it takes 12-16 weeks for a barrel to be made. I want to make sure I get it right the first time, but if I must miss then I rather be on the short side instead of long. You can always cut metal out but not cut it back in. Sorry for being long winded, but I wanted to be thorough. Any other advise would be welcome. Thanks for taking time to read and help.