I purchased those rounds from Midway usa last year and got curious about their warnings also. I didnt know. It took me to take the time and call their customer service and speak to a tech, who called me back from a Wisconsin phone # to tell me not to use them on ported or comp'd gun. It's true.
Pieces flying off and hitting the shooter or bystander were his words ; not mine. Not safe in ported or compensated guns were his warnings as well as the box.
I do realize that the 50 round boxes of ammo do not have these warnings! People should ask questions about the ammo they are shooting when in doubt.
I've been hit in the face by shooters next to me or sometimes shooting revolvers for years! Doesn't happen all the time, but I've bled from my neck, cheek hands by bullet fragments.
I've had bullet shavings smear off like paper. So the Speer/CCI warnings seem likely to me.

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