Hey fellas,

While seating 165 sie HPBT Gamekings in my 300WSM(Kimber) I try to seat .0020 off the lands. To accomplish this I seat the bullet long leaving rifling marks on the copper jacket. I then progressively seat the bullet deeper and deeper until they disappear. I think you all know what I'm talking about, not exact precision but close enought. Anyway, when the rifling marks disappear there still seems to be unusual marking on 1/4 the circumference of the bullet towards the bottom. Any suggestions?

if you blackken the bullet with a magic marker you will see some of it scrape off on the ramp or the neck area of the chamber, before the neck is fully chambered.
make a simple guage from a once fired case by split the neck so a bullet slides in and out with just a little resitance. carefully remove the case from the chamber and measure oal.

On a Kimber Montana it's very easy.
1. Put the safety lever at the middle setting. You can then open the action but the rifle would not fire.
2. Leaving the safety in that position, it's a simple matter of just unscrewing the rear of the bolt thus removing the firing pin.
3. Insert the bolt back into the rifle and try to chamber a cartridge whose bullet you know is too long.
4. Gradually seat the bullet deeper while all the time attempt to chamber the round.
5. When the round chambers, that is your max OAL.
6. Pull the bolt out of the rifle and screw the firing pin mechanism back into the bolt. Again, make sure the safety is in it's midway position. When you have fully inserted, the firing pin mechanism, you wil hear & feel a "click".
That's all there is to the Montana - straight forward & simple.
Bear in Fairbanks

Seating Bullets the easiest and most accurate way.

Best of luck to you.

I agree with hivelosity that it is probably a scrape mark from the ramp or neck area of the chamber. I frequently see the same thing in my guns.