mine jammed on any and all mil spec brass. and i mean jammed. on loading, so it was hairy extracting the round. the brass all measured to Saami specs .
i called Core and they told me their chambers are all "tight" and not to use mil spec brass.
my question was "so if i am in a scrap some where and happen to get mil spec ammo, i'm SOL?" their answer was yep!
the core barrel got replaced.
lost me as a customer.
I've fired many mil spec rounds through my Core M4 without any issues. I'm very pleased with it.
