Thread: "Air space" in 303 British and 308 Winchester caseloads...Dangerous?

@Kiwi Sapper

Concentricity of bullet seating refers to the bullet axis being concentric with the bore axis. Not a problem in round balls, but in long and pointy bullets it is. A oblong bullet engaging the rifling at an angle will, if you trace the progression of its very tip, progress in a corkscrew manner through the barrel, and on exiting fly in a corkscrew trajectory until the spin stabilises it ... at a random point in the corkscrew trajectory. And it flies straight from that point on. This theory predicts that if you zero your rifle at a particular point, bullets will tend to hit AROUND this point, and with less initial corkscrewing the smaller the ring diameter. That is, if you shoot 20 round groups, the groups should be less dense around their middles.

Back to @winaa's comment that he believes concentric rounds are more important than jump.