Newbie 6BR question

[waterfwlr]

I just bought a savage 6br LRPV and am starting to work up a load for it. As far as seating goes, I keep hearing about jumps and jams. I know what a jump is. But what is a jam. How would I get a .010 jam?

 

[GSRswapandslow]

find your rifling...then set the bullet seater to be 0.010" longer than that length. The bullet will be "jammed" into the lands of the rifling at that point.

 

[lrgoodger]

It took me a while to understand that subject when I started handloading. The point at which the bullet is just starting to touch the riflings is generally considered the zero point. Backing off from that (seating the bullet deeper into the case) is called jumping and the jump distance is measured back from the zero point. If you go the other way (seat the bullet further OUT of the case), it is called jamming because you are jamming the bullet into the lands. The distance is measured from the zero point as well, but it is called a jam instead of a jump. Now, an important factor in jamming is neck tension. If you have a very light neck tension, the bullet will quickly reach a point where you cannot jam it any deeper (I call it FULL jam) before the rifling starts pushing the bullet further into the case. If you have heavy neck tension, full jam will be much further into the lands because the grip of the neck on the bullet is such that the bolt can drive it quite deep (i.e., mark the bullet more heavily).

Hope this helps.

Ron

 

[waterfwlr]

That clears that up. Thanks guys. I appreciate it.