I developed a 165 gr load 35 years ago and have just loaded it. Now I'm developing a 180gr, Nosler Partition load for elk this fall.
I wasn't happy with the first swing so decided to get somewhat more formal and check how far the bullet was from the lands. What I found made me go back and do it about a dozen different ways. Always came up with the same.
I'm using the slight pressure on the neck and chamber the round to check it.
Distance from the base of the case to the lands is 2.834". I compared this against a scribed ring around the bullet and also seating a bullet backwards.
If I seat the Nosler 180gr Partition to the lands, the COAL is 3.495". This seems extremely long. If I seat the bullets out to within 020 to .050 of the lands, then the COAL will be in the neighborhood of 3.450" or 0.110" longer than what would seem correct.
When I developed the load 35 years ago, I used a COAL of 3.350". I noted during the load development that I could run over the max power with no signs of excessive pressure. My current load for the 165gr is 52.5 grains of 4064 powder.
I understand that I can load them out to 3.495 and still fit in my magazine on the Rem 700 ADL. So, I can load them to 3.075 and get .020 from the lands. However, they will not likely fit in anything else and would be unsafe, at best.
So, my question is, what has your experience been when dealing with freebore in the area of .150". Does the extra .110" negatively impact accuracy, or is it a trial method to see? If it is definite, then it might be time to justify another 30-06.