I used the Hornady device to measure my distance to the the lands. It gave me a distance of 2.618” to the bullet ogive. I then thought I would try something I saw on YouTube to decide how much jump you need to load for. I loaded up a dummy load with the bullet seated way out. I colored the bullet with a magic marker, I then chambered it. When I got it out it measured 2.645” to the ogive and 2.566” to where the marker was messed up. My question is how can these two methods be so different?
Method difference: The Hornady tool takes datum from shoulder contac
t in your chamber, while jamming is w/resp to bolt face
Whatever you seen on youtube cannot tell you how much jump you need to load for..
The only way to determine best cartridge base to ogive (CBTO) is through full seating testing.
That best result is not 'predictable' by anyone.
Also, Jam length does not produce touching, which distance off the lands (OTL) is based on.
Someone mentioned Alex Wheeler's method. He didn't invent it or anything, it's old tried & true.
But he did put out a great video for it:
Myself, I use a cleaning rod method to find touching. I only do it intially(new barrel) to give me a starting point for my range of seating testing. I don't ever do it again with a given barrel, and I never care where touching or jam really is.
All I care about is the CBTO that testing tells me is best.
CBTO is not w/resp to lands, so that's why I don't care about what my land relationship is.
Honestly, we make way too much of finding touching land relationship with dead nutz accuracy, as it really doesn't matter at all..