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amamnn · December 25, 2006, 02:11 AM

In ye olden days we referred to the length that the bullet was run out of the case as runout. These days, people use runout as a sort of generic term for misalignment of various components in a cartridge. So now we're stuck with the term seating depth which is a backward way of describing how far in or out of the case you've left your bullet when you are done loading the cartridge. You want your bullet seated in the neck far enough in that you can maintain proper tension (the grip of the case neck upon the bullet) on the bearing surface of the bullet. Unfortunately for those who want to use the popular benchrester's method of seating the bullet out to the lands of the barrel, factory rifles have chambers that make the method largely ineffective if not impossible.

If you have the knowledge and the tools to measure the chamber of your rifle and the base to ogive length of your bullets, and head to ogive length of your cartridges, you'll have a good idea of how far out you need to seat in order to approach or get into the lands of the barrel. Most times, just going for long seating without ensuring concentricity (alignment, or runout) of the neck inside and out and the chamber/barrel of the rifle results in no improvement as the bullet has to bounce around to find the center of the lands.

Without controlling the above variables, long seating is mostly just guesswork and if you get a real improvement it's mainly luck.

December 25, 2006, 02:11 AM	#3
amamnn Senior Member Join Date: May 13, 2006 Location: WA, the left armpit of the USA Posts: 1,323	In ye olden days we referred to the length that the bullet was run out of the case as runout. These days, people use runout as a sort of generic term for misalignment of various components in a cartridge. So now we're stuck with the term seating depth which is a backward way of describing how far in or out of the case you've left your bullet when you are done loading the cartridge. You want your bullet seated in the neck far enough in that you can maintain proper tension (the grip of the case neck upon the bullet) on the bearing surface of the bullet. Unfortunately for those who want to use the popular benchrester's method of seating the bullet out to the lands of the barrel, factory rifles have chambers that make the method largely ineffective if not impossible. If you have the knowledge and the tools to measure the chamber of your rifle and the base to ogive length of your bullets, and head to ogive length of your cartridges, you'll have a good idea of how far out you need to seat in order to approach or get into the lands of the barrel. Most times, just going for long seating without ensuring concentricity (alignment, or runout) of the neck inside and out and the chamber/barrel of the rifle results in no improvement as the bullet has to bounce around to find the center of the lands. Without controlling the above variables, long seating is mostly just guesswork and if you get a real improvement it's mainly luck.