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Understanding Jumping and Jamming a Bullet

   Regarding reloading techniques, jamming or jumping a bullet relates to the seating depth of the bullet during loading and its   distance from the rifling of your barrel when chambered. Seating depths are commonly referred to as either jump or jam   distances. Jump relates to the distance from the lands of the rifling (the raised ridges of metal inside the rifle barrel), 

 while jam refers to the distance into the rifling that you push the bullet when you chamber a round by closing your bolt.

   Reference to Ammerman Arms’ 6mm 68Gr HPBT and 6mm 68Gr HPFB:

  Example, .035 Freeboard may need to be jumped or jammed starting at .005