The boxes are an off white color.The PMC can't be all that old. Is the Super X .22lr in yellow or white boxes?
I have white box stuff that's still good (better than the new Winchester rim fires!).
Try shooting samples of the factory ammo but keep a squib rod handy in case it's not up to snuff.
Pull what's problematic for the primed brass and projectiles.
4th of July will be here some enough for fireworks.