7-08 Help

[Outdrmn]

In essence yes, but I will be more detailed just to be sure we are on the same page. I always start from in the magazine and go as long as possible to establish my OAL and record that CBTO*. If I am having a chamber cut I'll send in a dummy round of that CBTO and ask for a 20K jump to the lands. Obviously, at this point I am already seated as long I can in my mag and playing with seating depths will only increase my jump as I seat the bullet deeper in the case.

However, if your chamber is already cut you don't have that option. But you still need to know your CBTO from a mag length OAL and you still want to know where your lands are. You have two choices to find out where your lands are; you can use an OAL gauge and modified case or field strip your bolt and follow Alex Wheeler's method. I find that his method is more precise than the OAL gauge.

*I should not assume you realize the ogive is different between a 162 ELDM vs a similar weight bullet in say a Berger or Nosler. Which is why you have to use the same bullet when setting all this up.

Hope that clears things up

Yes, very clear and detailed! Thanks for sharing your wisdom and experience!

 

[MAD10]

Great glad to help! btw I assume you already have a chamber cut and you are working backwards "so to speak" if so, do not be too alarmed if you discover your jump is more than what is considered "normal"

There is quite a few guys running jump tests today and we are learning many of us put too much emphasis in jump. ALL THINGS BEING EQUAL the jump has very little to do with accuracy or ES. Of much more importance is the overall concentricity and consistency of the cartridge (factory or your own) and the alignment of your bore to your chamber.

Case in point, I had a chamber cut to have a 20 thou jump with oberndorf bottom metal. Later, I decided to switch to Hawkins bottom metal with dbms....since I had to seat the bullets further in the case to fit in the dbms my jump increased by 60 thou. Fortunately for me it made no difference if I was 20 or 80 K off the lands...I still saw similar velocities and accuracy.

 

[Orange Dust]

Great glad to help! btw I assume you already have a chamber cut and you are working backwards "so to speak" if so, do not be too alarmed if you discover your jump is more than what is considered "normal"

There is quite a few guys running jump tests today and we are learning many of us put too much emphasis in jump. ALL THINGS BEING EQUAL the jump has very little to do with accuracy or ES. Of much more importance is the overall concentricity and consistency of the cartridge (factory or your own) and the alignment of your bore to your chamber.

Case in point, I had a chamber cut to have a 20 thou jump with oberndorf bottom metal. Later, I decided to switch to Hawkins bottom metal with dbms....since I had to seat the bullets further in the case to fit in the dbms my jump increased by 60 thou. Fortunately for me it made no difference if I was 20 or 80 K off the lands...I still saw similar velocities and accuracy.

Yes, as a general rule the smaller the capacity, the more tolerant cartridges are of such things.