Thread: Trying something, Eric Cortina method of load development

Originally Posted by Dead is better

Ironically he's just swapped one "moving target" for another. Because what is 'jam'? One case with its own neck tension and runout will never leave the bullet in the exact location as any other case on earth.
Might as well use the 'just touch' method and take an average if you're looking to be super precise.

No, that is incorrect. For the purposes of getting started with load testing, 'jam' is the point beyond which a projectile will stick in the rifling and stay behind if a loaded round is removed from the chamber. He never references this point after an initial measurement. It is a practical safety step to avoid a problematic situation.

The take away message of the video is not to try to measure where the lands are as this is futile (this is a moving target for sure). The whole point of the video is to show a methodology to let the target tell you what seating depth is best. By identifying the closest point to the rifling at which there is a 'tiny group node' to use as your initial length, you maximise your time shooting groups in that window.

After you've shot a bunch of rounds you load 5 rounds at the accurate length plus 3 thousandths to see if the window of accurate lengths has moved. There is no more measuring. Shoot a group to see if the lands have moved.

The only absolute is the base to ogive of a loaded round - this is easily measured.