OCW load development - what is meant by "a caliber's depth"?

[Bob 964]

In Dan Newberry's instructions for OCW load development (reference step #6), he recommends seating the bullet "a caliber's depth" into the case, or to magazine length--whichever is shorter. Can someone tell me what is meant by the term "a caliber's depth"? Thanks.
Bob

 

[arnie19]

I would guess if your loading a .308 bullet then you should put the bearing area of the bullet .308 into the neck of the case . By bearing area im saying not to count the boat tail as part of the seated depth.

 

[damoncali]

For whatever reason, it's common to refer to things like rifle barrels and twist rates in terms of calibers - engineers like this kind of thing because it keeps things general. (In BRL/APG/etc papers and old ballistics books you'll often see twist rates in units of calibers instead of inches - that sort of thing). So yeah, he means exactly what arnie19 says.

That said, you can get away with a little less if you have to. A caliber's worth is a good rule, though.

 

[Twoboxer]

Since a reasonable seating depth would vary based on bullet width and length, the rule of thumb "a caliber's depth" is thought to be sufficient to maintain neck tension and concentricity given reasonable handling.

So the seating depth would vary by caliber; 223 set ~0.223" deep, 30-06 set ~0.308" deep, etc.