Quote:
Originally Posted by 338Bluff
Seating the bullets way out may mislead some people, in that they believe that this adds a lot of capacity to the cartridge case. The reality is, the effective chamber volume is the volume with the bullet against the lands, as that is where the pressure really starts to climb. That is why extra freebore allows you to gain some velocity with the same peak pressure. It doesn't take much to drive a bullet out of the case, so this happens very quickly, before the pressure climbs anywhere near peak. When the bullet reaches the lands, and the lands must engrave the bullet, the pressure climbs rapidly. And seating right on the lands, actually increases the pressure, because the bullet has less momentum when it strikes the lands, so it takes more effort for the lands to engrave the
Sort of knew that. However, the guy making the claim likely knows that as well. I'm not a gunsmith or a ballastician but the guy making the claim has the credentials. I don't think a 12 minute clip on you tube video that also touches on 5 or 6 other cartridges provides the detail. Likely more to the story.
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I think that it's simply a matter of he kept adding powder until he reached that load, no blown primers, and the bolt wasn't that hard to open, so to him it's safe in his rifle. That is how some old school people still think.
When I received my current 7mmstw from my gunsmith, I worked up some loads right out of the Barnes manual. No obvious pressure signs until I ran them over the chronograph, and I saw over 3600fps with the 140gr TTSX. That was nearly 150fps more than the velocity in the manual, and 100fps more than I saw in my other five previous rifles, as well as .0015" expansion on the belt. I dropped two grains, for 3500fps, and the belt expansion dropped to under .0005".