tobnpr's comment about a lightly seated bullet that will just get shoved into the case, compressing the load and causing quite a "moment" for the shooter, and the rest of the firing line. . . .
Consider the fact that competitive shooters loading ammo for single loading in slow fire matches have been "light seating" bullets for decades. With max loads at normal peak pressures, there's no increase in peak pressure that'll make things unsafe.
Yes, those bullets will be shoved back into the case. But a dozen or two thousandths of bullet setback when chambered is nothing. If that's thought to be a problem, consider the fact that there's no significant peak pressure difference from a new barrel's effect on a given load compared to several thousand rounds later when its leade has lengthened 1/10 inch or more from erosion. Besides, few, if any, safe max loads have 100% loading density anyway, so seating the bullet back a bit when chambered is no big deal.
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