*CAUTION* Never load cases from an unknown source, i.e. cases picked up at the range or sold as once fired brass.
*CAUTION* Load only cases which you have obtained as new unfired brass or which you have on hand as the result of firing new factory ammo in the firearm for which you wish to reload. A few pennies saved on bargain so called "once-fired" brass makes little sense when one considers the cost of a firearm and/or medical treatment, or wose....
Considering how many hand loaders have bought and used such brass with no problems reported, the warnings not to do so, fit the category of: It sounds
like good advice, but statistics indicate otherwise. Just because the author wrote it, does not make it true.
Consider handgun brass that has been hand loaded many times...It usually cracks at the mouth and the hand loader then discards it. I hand load my brass over and over until the individual piece fails and then I discard it...just that piece. A catastrophic failure is not imminent just because a piece of brass has been hand loaded before, or many times before.
With rifle cases, an incipient head separation can be detected before
it happens. Although I would not pickup range brass (or buy it), because with a rifle, I want to start with new, unfired brass from the same lot, for accuracy purposes.