I look forward to that article too JB.
Currently working with a 7x57, economy A&B 21" bbl ( I was gifted several vz-24 recievers, A&B bbls in various chamberings, reamers, go/nogo gages, Timney triggers, sporter stocks, & so forth). Dyna coated the bore due to the A&B bore is very prone to copper foul.
Anyhow, worked w/ Hornady 139 IL & Nosler 150 BT. Goal is to get some background w/ Nosler BT, then work with 150 Nosler Accubonds for the final load.
Seated the Hornady to 3" oal, per Hornady book. I did the slit case neck, start bullet, push case in chamber until case shoulder butts chamber shoulder. OAL =3.080". Hornady 139IL jump is ~0.080". 2700 fps per crono, makes 1 3/4" @ 100.
Nosler 150 BT seated to 3.070" (SAMII max is 3.065" per Nosler book). I did the slit case neck, start bullet, push case in chamber until case shoulder butts chamber shoulder. OAL =3.150".
I conclude that the Nosler 150 BT is jumping ~0.080". This shoots ~1.00-1.25" @ 100 yard. W/49gr IMR 4350 makes 2815 fps per crono.
Intuition tells me to jump the Nosler BT a bit less, say 0.050" using same powder weight. Given I'm working with an A&B barrel, could be that 1" 3-5 shot groups could be all I can expect.
I've always approached seating depth (bullet jump) as trial & error. I'll say it again, looking forward to that article JB.
Pat
You need to realize that once you start working with custom throats rather than SAAMI-spec throats, all those max COAL suggestions go out the window. They give you those max COAL numbers to guarantee that your ammo will fit in any SAAMI chamber. If you're loading for a particular rifle, you can determine your own max COAL by finding where the bullet contacts the rifling, and then the max COAL that I've commonly seen and used, is 0.030" into the lands, and that's typically only used for BR-type shooting. That would be the max, but reliability may suffer with that deep of a jam, so you may want to consider 0.010" into the rifling (or until the rifling makes a square engraving mark on the bullet when the cartridge is chambered) as max COAL for reliable hunting and field ammunition. Then work backward until you find optimal accuracy.
Of course, this hinges on you having enough magazine box length to accommodate these max OAL's, and if not, then your mag box max length, minus about 0.010-0.020", becomes your max COAL for a repeater. If you don't mind feeding the rifle as a single shot, then mag box constraints are irrelevant.
