Pharmseller suggested I try some Nosler BTs , so I bought some 140 gr.
Before I ran a test with Sierra 120 spt , I measured a max COAL of 2.781", with the 140
gr BTs I have a max coal of 2.918".

I know SAAMI is 2.800" and Nosler lists 2.800" as well but that would put me at a 0.118"
jump.
For those of you that run this bullet , what jump are some of you loading ?

I figured I needed to have a longer bullet to get closer to the lands , have enough bearing
surface in the neck and not protrude too far into the powder.

Thanks in advance, WT.

First and foremost, what is your magazine box length? I generally go as long as the mag will allow if I'm not hitting lands. This assumes a bullet has sufficient shank length to allow for adequate grip by the case neck (I'd not load something like the 100gr HP out as far as I could, as there would be basically nothing left in the neck....)

What JPro said; I haven't ever paid any attention to COAL specs in manuals unless mag confines sucked and I was at risk of being uber minimum in which case I changed bullets or rebarreled.

Thanks JPro and Efw, making a dummy, I kept seating till the tip was about
an 1/8 th or 3/16 th shy of touching the forward part of floor plate mag box.

With this 140 gr bt , the base of the boat tail is in line with beginning of the shoulder , before it tapers.

This gives me a 0.092" jump to the lands.

One of my 7mm-08 works best with a jump of 0.110" with the 140gr BT. Not my choice, but I'm limited by magazine and throat length. Luckily, I found that a relatively long jump will work.

Thank you ! That would put me at 2808

My 7mm-08 (Kimber Montana) has a magazine length of 2.83" and a chamber length of 2.882 (with 140 gr. BT). My load that is the most accurate has an OAL of 2.815" so a jump of .067". Closer to the lands might shoot as well but as you can see I am limited by the magazine. I am perfectly happy though with three shot groups (I know) of .75". As far as OAL, I have found that when a rifle will allow, best accuracy shows up when close to the lands and goes away as the cartridge gets shortened. However, there is usually another tightening of groups at some point as the jump gets longer.

My accuracy load, regardless of bullet, is 2.806" plus or minus a thousandth.

Weird.








Same rifle, three different bullets.





P

With Cup and Core bullets I start off with a .020 jump if magazine length allows. With Barnes it is .050.