Originally Posted By dodpilot:
So, do I crimp for ultra reliability in the field, in case I have to chamber and unchamber rounds multiple times?
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Bullet setback is from the rounds in the magazine subject to repeated recoil and this causing the bullets to slam into the magazine box's front wall, pushing them further into the case.
Setback, in this case, is not from repeated chambering and unchambering. The vast majority of rifle cartridges headspace off of the shoulder or a belt, so the bullet, unless in contact with the lands, isn't gonna be pushed back.
Topping off and not firing the rounds in the bottom of the mag is the basic underlying problem. That said, I read, but can't find it right now, that some setback occurs in some cartridges regardless of how much you crimp them. IIRC, the 416 Rigby was one that was particularly prone to setback, regardless of amount of crimp.