Yep, that's one of the reasons that no barrel air guages perfectly.
What I wrote is just rules of thumb that have came from speaking to many BR shooters with Hundreds of barrels each under belts, and still this is just a majority, not a full consensus. I only go through six to seven barrels a year, mostly cut rifled. I see the BT/cut rifled theory pan out 95% (give or take) of the time.
What I mean by full jam is the measurement from the base of a case to the ogive with a bullet comparator (same comparator every time), with the bullet being pushed back in the case. I have used every method possible on establishing a reference OAL and the only way that is exceptable to me is the full jam. Now I here this, well cases work harden, neck tension, etc. When I make a new set of cases up (usually a 100 + at a time), I make extras I call seating cases. Two of these cases are marked and stay with a barrel it's whole life and are used for nothing but referencing jam and throat/leade wear. Now, many may ask how I came to the conclusion that Full Jam was best. Well, it took quite awhile and many trips to a friend tooling company using his optical comparator in order to see what works best. Full Jam is repeatable to around .0008 to .0012 , the other methods was around .005-.015 in tolarance. The second catagory included the stoney point, hornady gauge, blue dye, polished bullet, marker, and split case neck. The tolarances I listed are off the top of my head so they may not be exactly what I found. The thing with leades that has to be taken into account, is that once they wear past a certain point, the angle can really start to change. Some leades will seem to wear in a fairly consistant fashion as it pertains to the angle, others (I'm assuming due to the steal), will change more quickly. I have had one barrel that wanted to stop shooting after the throat had only moved .0015, adjusting .002 in either direction did not help, I ended up with a .008 move away from the leade to get it to shoot again. In this barrel, it seemed that the transition from the leade to the lands and from the freebore to the leade, rounded in a very pronouced manner (in a hump). The barrel quit completely within about 250 more rounds. Weird.
Hovis
What I wrote is just rules of thumb that have came from speaking to many BR shooters with Hundreds of barrels each under belts, and still this is just a majority, not a full consensus. I only go through six to seven barrels a year, mostly cut rifled. I see the BT/cut rifled theory pan out 95% (give or take) of the time.
What I mean by full jam is the measurement from the base of a case to the ogive with a bullet comparator (same comparator every time), with the bullet being pushed back in the case. I have used every method possible on establishing a reference OAL and the only way that is exceptable to me is the full jam. Now I here this, well cases work harden, neck tension, etc. When I make a new set of cases up (usually a 100 + at a time), I make extras I call seating cases. Two of these cases are marked and stay with a barrel it's whole life and are used for nothing but referencing jam and throat/leade wear. Now, many may ask how I came to the conclusion that Full Jam was best. Well, it took quite awhile and many trips to a friend tooling company using his optical comparator in order to see what works best. Full Jam is repeatable to around .0008 to .0012 , the other methods was around .005-.015 in tolarance. The second catagory included the stoney point, hornady gauge, blue dye, polished bullet, marker, and split case neck. The tolarances I listed are off the top of my head so they may not be exactly what I found. The thing with leades that has to be taken into account, is that once they wear past a certain point, the angle can really start to change. Some leades will seem to wear in a fairly consistant fashion as it pertains to the angle, others (I'm assuming due to the steal), will change more quickly. I have had one barrel that wanted to stop shooting after the throat had only moved .0015, adjusting .002 in either direction did not help, I ended up with a .008 move away from the leade to get it to shoot again. In this barrel, it seemed that the transition from the leade to the lands and from the freebore to the leade, rounded in a very pronouced manner (in a hump). The barrel quit completely within about 250 more rounds. Weird.
Hovis
