Pressure relative to distance from lands.
Hello, I've been wondering about this for awhile. I know that pressure is high when the bullet is jammed into the lands, and I know that when the bullet is seated deeper into the case, pressure is raised because of the decreased internal capacity of the case.
I've been curious if there is a certain sweet spot where pressure is low, and I can still load the bullet out long to save room in the case for powder. I was looking for some info on a 308 Win. I'm gonna be loading for in the spring, and I found this bit of info at 6mmbr.com.
" When choosing a load to test, keep in mind that seating depths can make a HUGE difference in pressure. Remember that seating bullets into the lands can raise pressures but moving 0.020" or more AWAY from the lands can also raise pressures, because you are reducing the effective case capacity. Many readers ask us "should I jam or jump my bullets." There is no right answer for every gun. For every guy getting great results at .015" jam, there is another guy doing well with a 0.025" jump. In general, most popular .308 match bullets (Bergers excepted) are tolerant of jump. This is certainly true of the 168 and 175 SMKs. So don't worry that you may be sacrificing a great deal of accuracy by loading to mag length, even if that puts you pretty far from the lands."
The way it looks to me is that people are seeing the sweet spot I'm looking for at the 0.020" off the lands mark.
Has anybody here experienced this??
I want to apply this to the 308 Win. by loading heavier bullets in a 30" 1-10 twist barrel. I'd like to use a powder that fills the case right up to the base of the bullet, or slightly compressed. But, I would like to know it just because, and I'd apply it to others as well.