Someone please explain freebore Vs jump

[Never Forget]

Maybe I am over thinking this but I still seem to be confused on freebore. I have found several discussions on freebore and I believe I understand what it is but to me it still sounds just like jump. And with most people jamming bullets to some extent my simple brain thinks the less freebore the better. I just ordered everything for my build and have several months before the gun is chambered but want to get my head wrapped around this.

I think the reason I am so concerned is I have a Rem 700 in 300 win mag 5r Barrel, it came to me new with .220 of jump (thank you Remington) using 190 Bergers. I came up with that # going from Saami spec to touching the lands. I have only 700 rounds fired and have lost an additional .060 of throat so far. Sierra 175's fall out of the case before I can touch the lands and get a measurement. Cant help but think this barrel wont shoot to my expectations much longer so I ordered a barrel for this gun today. To be fair to Remington this gun did shoot 1/2 MOA all day and 1/4 Moa after I had the action bedded, but now has dropped back to 1/2 as I chase the throat.

I'm building a 6br, Krieger 8" twist, and hoping to run 105 Bergers. I have read that about a .105 freebore is what is recommended for these bullets. So am I handicapping myself with a .105 jump right off the bat with a .105 freebore?

Thanks in advance, John

 

[bsumoba]

Freebore is the space that exists in the bore that does not have rifling

Jump is the amount of distance the bullet travels before it engages the rifling

Here are some vids that will explain it:

https://www.youtube.com/watch?v=IVltKuzVBMw&index=23&list=PLCD31A83F7643E23C

https://www.youtube.com/watch?v=J3OikVyRGTg

 

[dkhunt14]

Freebore gets the bullet pressure ring out of the base of the shoulder neck junction. It is not a good thing for accuracy to push the pressure ring through the sized part of the neck. I am not sure what freebore the 6 BR uses but in my Dasher I run a .155 freebore and it puts the pressure ring about halfway up the neck with .010 in the lands. Most people seem to run a .135 in a Dasher but the BR will be different. Jump is the distance you are away from the lands with the bullet. Matt